Hemant K Chitale
I am an Oracle Database Specialist in Singapore.
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Updated: 3 months 3 days ago
Backup and Restore a Standby Database
I have seen some I.T. managers that decide to backup only the Primary Database and not the Standby. The logic is "if the Storage or Server for the Standby go down, we can rebuild the database from the Primary". OR "we haven't allocated storage / tape drive space at the Standby site" OR "our third-party backup tool does not know how to backup a Standby database and handle the warning about Archive Logs that is generated when it issues a "PLUS ARCHIVELOG" {see the warning below when I run the backup command)
Do they factor the time that is required to run Backup, Copy, Restore commands OR run the Duplicate command to rebuild the Standby ? All that while their Critical database is running without a Standby -- without a D.R. site.
Given a moderately large Database, it can be faster to restore from a "local" Backup at the Standby then to copy / duplicate across the network. Also, this method does NOT require rebuilding DataGuard Broker configuration.
Firstly, you CAN backup a Standby even while Recovery (i.e. Redo Apply) is running. The only catch is the "PLUS ARCHIVELOG" clause in "BACKUP ... DATABASE PLUS ARCHIVELOG" returns a minor error because a Standby cannot issue "ALTER SYSTEM ARCHIVE LOG CURRENT" (or "ALTER SYSTEM SWITCH LOGFILE")
Here's my Backup command at the Standby (while Redo Apply -- i.e. Media Recovery -- is running) without issuing a CANCEL RECOVERY.
RMAN> backup as compressed backupset 2> database 3> format '/tmp/STDBY_Backup/DB_DataFiles_%U.bak' 4> plus archivelog 5> format '/tmp/STDBY_Backup/DB_ArchLogs_%U.bak'; .... .... RMAN> backup current controlfile 2> format '/tmp/STDBY_Backup/standby_controlfile.bak';
So, when I run the Backup, it starts of with and also ends with :
RMAN-06820: warning: failed to archive current log at primary database cannot connect to remote database .... .... .... RMAN-06820: warning: failed to archive current log at primary database cannot connect to remote database using channel ORA_DISK_1 specification does not match any archived log in the repository backup cancelled because there are no files to backup
because it cannot issue an "ALTER DATABASE ARCHIVE LOG COMMAND" -- which can only be done at a Primary. These warnings do not trouble me.
A LIST BACKUP command at the Standby *does* show Backups created locally (it will not show Backups at the Primary unless I connect to the same Recovery Catalog that is being used by the Primary) ( I have excluded listing each ArchiveLog / Datafile from the output here)
So I can confirm that I have *local* backups (including ArchiveLogs present at the Standby and backed up before the Datafile backup begins). The last ArchiveLog backed up at the Standby is SEQ#394 for Thread#1 and SEQ#339 for Thread#2
RMAN> list backup;
list backup;
using target database control file instead of recovery catalog
List of Backup Sets
===================
BS Key Size Device Type Elapsed Time Completion Time
------- ---------- ----------- ------------ ---------------
311 44.10M DISK 00:00:02 01-MAY-25
BP Key: 311 Status: AVAILABLE Compressed: YES Tag: TAG20250501T074832
Piece Name: /tmp/STDBY_Backup/DB_ArchLogs_ad3objeg_333_1_1.bak
List of Archived Logs in backup set 311
Thrd Seq Low SCN Low Time Next SCN Next Time
---- ------- ---------- --------- ---------- ---------
1 393 11126161 01-MAY-25 11126287 01-MAY-25
1 394 11126287 01-MAY-25 11127601 01-MAY-25
...
...
2 338 11126158 01-MAY-25 11126290 01-MAY-25
2 339 11126290 01-MAY-25 11127596 01-MAY-25
BS Key Type LV Size Device Type Elapsed Time Completion Time
------- ---- -- ---------- ----------- ------------ ---------------
312 Full 1.07G DISK 00:00:57 01-MAY-25
BP Key: 312 Status: AVAILABLE Compressed: YES Tag: TAG20250501T074835
Piece Name: /tmp/STDBY_Backup/DB_DataFiles_ae3objej_334_1_1.bak
List of Datafiles in backup set 312
File LV Type Ckp SCN Ckp Time Abs Fuz SCN Sparse Name
---- -- ---- ---------- --------- ----------- ------ ----
....
....
BS Key Type LV Size Device Type Elapsed Time Completion Time
------- ---- -- ---------- ----------- ------------ ---------------
313 Full 831.00M DISK 00:00:43 01-MAY-25
BP Key: 313 Status: AVAILABLE Compressed: YES Tag: TAG20250501T074835
Piece Name: /tmp/STDBY_Backup/DB_DataFiles_af3objgk_335_1_1.bak
List of Datafiles in backup set 313
Container ID: 3, PDB Name: PDB1
File LV Type Ckp SCN Ckp Time Abs Fuz SCN Sparse Name
---- -- ---- ---------- --------- ----------- ------ ----
....
....
BS Key Type LV Size Device Type Elapsed Time Completion Time
------- ---- -- ---------- ----------- ------------ ---------------
314 Full 807.77M DISK 00:00:42 01-MAY-25
BP Key: 314 Status: AVAILABLE Compressed: YES Tag: TAG20250501T074835
Piece Name: /tmp/STDBY_Backup/DB_DataFiles_ag3obji1_336_1_1.bak
List of Datafiles in backup set 314
Container ID: 5, PDB Name: TSTPDB
File LV Type Ckp SCN Ckp Time Abs Fuz SCN Sparse Name
---- -- ---- ---------- --------- ----------- ------ ----
....
....
BS Key Type LV Size Device Type Elapsed Time Completion Time
------- ---- -- ---------- ----------- ------------ ---------------
315 Full 807.75M DISK 00:00:43 01-MAY-25
BP Key: 315 Status: AVAILABLE Compressed: YES Tag: TAG20250501T074835
Piece Name: /tmp/STDBY_Backup/DB_DataFiles_ah3objje_337_1_1.bak
List of Datafiles in backup set 315
Container ID: 2, PDB Name: PDB$SEED
File LV Type Ckp SCN Ckp Time Abs Fuz SCN Sparse Name
---- -- ---- ---------- --------- ----------- ------ ----
....
....
BS Key Type LV Size Device Type Elapsed Time Completion Time
------- ---- -- ---------- ----------- ------------ ---------------
317 Full 19.58M DISK 00:00:01 01-MAY-25
BP Key: 317 Status: AVAILABLE Compressed: NO Tag: TAG20250501T075522
Piece Name: /tmp/STDBY_Backup/standby_controlfile.bak
Standby Control File Included: Ckp SCN: 11128626 Ckp time: 01-MAY-25
RMAN>
So I can confirm that I have *local* backups (including ArchiveLogs present at the Standby and backed up before the Datafile backup begins). The last ArchiveLog backed up at the Standby is SEQ#394 for Thread#1 and SEQ#339 for Thread#2
Meanwhile, the Standby has already applied subsequent ArchiveLogs as Recovery had not been cancelled.
Now I simulate loss / corruption of the filesystem holding the Standby datafiles and controlfiles and attempt a Restore (if the Standby Redo Logs are also lost, I must add them again later before I resume recovery).
I do a SHUTDOWN ABORT at the Standby if he instance seems to be running.
(not shown here)
First I stop Redo Shipping from the Primary
Next I Restore the *standby* controlfile at my Standby server (note that I connect to "target" and specify "standby controlfile"). Note : If my SPFILE or PFILE is not available at the Standby, I have to restore that as well before I STARTUP NOMOUNT.
In this case, the Standby Controlfile backup was taken *after* the Datafile and ArchiveLog backups, so this Controlfile is already "aware" of the backups (they are already included in the controlfile). Neverthless, I can do some verification : ( I have excluded listing each ArchiveLog / Datafile from the output here)
For good measure, I can also verify that this "database" is a Standby (only the controlfile is presently restored" is a *Standby Database* (that a database is a Primary or a Standby is information in the *Controlfile*, not in the Datafiles)
I can return to RMAN and RESTORE the Database. (I still invoke RMAN to connect to "target", not "auxiliary"
Next, I restore the ArchiveLogs that I have in the local backup instead of having to wait for them to be shipped from the Primary during the Recover Phase
DGMGRL> connect sys Password: Connected to "RACDB" Connected as SYSDBA. DGMGRL> EDIT DATABASE 'RACDB' SET STATE='TRANSPORT-OFF'; Succeeded. DGMGRL>
Next I Restore the *standby* controlfile at my Standby server (note that I connect to "target" and specify "standby controlfile"). Note : If my SPFILE or PFILE is not available at the Standby, I have to restore that as well before I STARTUP NOMOUNT.
[oracle@stdby ~]$ rman target / Recovery Manager: Release 19.0.0.0.0 - Production on Thu May 1 08:27:23 2025 Version 19.25.0.0.0 Copyright (c) 1982, 2019, Oracle and/or its affiliates. All rights reserved. connected to target database (not started) RMAN> startup nomount; startup nomount; Oracle instance started Total System Global Area 2147480256 bytes Fixed Size 9179840 bytes Variable Size 486539264 bytes Database Buffers 1644167168 bytes Redo Buffers 7593984 bytes RMAN> restore standby controlfile from '/tmp/STDBY_Backup/standby_controlfile.bak'; restore standby controlfile from '/tmp/STDBY_Backup/standby_controlfile.bak'; Starting restore at 01-MAY-25 using target database control file instead of recovery catalog allocated channel: ORA_DISK_1 channel ORA_DISK_1: SID=310 device type=DISK channel ORA_DISK_1: restoring control file channel ORA_DISK_1: restore complete, elapsed time: 00:00:01 output file name=/Standby_DB/oradata/control01.ctl output file name=/Standby_DB/FRA/control02.ctl Finished restore at 01-MAY-25 RMAN>I am now ready to CATALOG the Backups and RESTORE the Database
RMAN> alter database mount; alter database mount; released channel: ORA_DISK_1 Statement processed RMAN> catalog start with '/tmp/STDBY_Backup'; catalog start with '/tmp/STDBY_Backup'; Starting implicit crosscheck backup at 01-MAY-25 allocated channel: ORA_DISK_1 channel ORA_DISK_1: SID=11 device type=DISK Crosschecked 13 objects Finished implicit crosscheck backup at 01-MAY-25 Starting implicit crosscheck copy at 01-MAY-25 using channel ORA_DISK_1 Finished implicit crosscheck copy at 01-MAY-25 searching for all files in the recovery area cataloging files... no files cataloged searching for all files that match the pattern /tmp/STDBY_Backup List of Files Unknown to the Database ===================================== File Name: /tmp/STDBY_Backup/standby_controlfile.bak Do you really want to catalog the above files (enter YES or NO)? YES cataloging files... cataloging done List of Cataloged Files ======================= File Name: /tmp/STDBY_Backup/standby_controlfile.bak RMAN>
In this case, the Standby Controlfile backup was taken *after* the Datafile and ArchiveLog backups, so this Controlfile is already "aware" of the backups (they are already included in the controlfile). Neverthless, I can do some verification : ( I have excluded listing each ArchiveLog / Datafile from the output here)
RMAN> list backup ;
list backup ;
List of Backup Sets
===================
BS Key Size Device Type Elapsed Time Completion Time
------- ---------- ----------- ------------ ---------------
311 44.10M DISK 00:00:02 01-MAY-25
BP Key: 311 Status: AVAILABLE Compressed: YES Tag: TAG20250501T074832
Piece Name: /tmp/STDBY_Backup/DB_ArchLogs_ad3objeg_333_1_1.bak
BS Key Type LV Size Device Type Elapsed Time Completion Time
------- ---- -- ---------- ----------- ------------ ---------------
312 Full 1.07G DISK 00:00:57 01-MAY-25
BS Key Type LV Size Device Type Elapsed Time Completion Time
------- ---- -- ---------- ----------- ------------ ---------------
313 Full 831.00M DISK 00:00:43 01-MAY-25
BS Key Type LV Size Device Type Elapsed Time Completion Time
------- ---- -- ---------- ----------- ------------ ---------------
314 Full 807.77M DISK 00:00:42 01-MAY-25
BS Key Type LV Size Device Type Elapsed Time Completion Time
------- ---- -- ---------- ----------- ------------ ---------------
315 Full 807.75M DISK 00:00:43 01-MAY-25
BS Key Type LV Size Device Type Elapsed Time Completion Time
------- ---- -- ---------- ----------- ------------ ---------------
316 Full 19.61M DISK 00:00:01 01-MAY-25
BS Key Type LV Size Device Type Elapsed Time Completion Time
------- ---- -- ---------- ----------- ------------ ---------------
317 Full 19.58M DISK 00:00:01 01-MAY-25
BP Key: 317 Status: AVAILABLE Compressed: NO Tag: TAG20250501T075522
Piece Name: /tmp/STDBY_Backup/standby_controlfile.bak
Standby Control File Included: Ckp SCN: 11128626 Ckp time: 01-MAY-25
RMAN>
For good measure, I can also verify that this "database" is a Standby (only the controlfile is presently restored" is a *Standby Database* (that a database is a Primary or a Standby is information in the *Controlfile*, not in the Datafiles)
RMAN> exit exit RMAN Client Diagnostic Trace file : /u01/app/oracle/diag/clients/user_oracle/host_4144547424_110/trace/ora_4560_140406053321216.trc Recovery Manager complete. [oracle@stdby ~]$ sqlplus / as sysdba SQL*Plus: Release 19.0.0.0.0 - Production on Thu May 1 08:37:54 2025 Version 19.25.0.0.0 Copyright (c) 1982, 2024, Oracle. All rights reserved. Connected to: Oracle Database 19c Enterprise Edition Release 19.0.0.0.0 - Production Version 19.25.0.0.0 SQL> select open_mode, database_role from v$database; OPEN_MODE DATABASE_ROLE -------------------- ---------------- MOUNTED PHYSICAL STANDBY SQL>
I can return to RMAN and RESTORE the Database. (I still invoke RMAN to connect to "target", not "auxiliary"
SQL> exit Disconnected from Oracle Database 19c Enterprise Edition Release 19.0.0.0.0 - Production Version 19.25.0.0.0 [oracle@stdby ~]$ rman target / Recovery Manager: Release 19.0.0.0.0 - Production on Thu May 1 08:40:32 2025 Version 19.25.0.0.0 Copyright (c) 1982, 2019, Oracle and/or its affiliates. All rights reserved. connected to target database: RACDB (DBID=1162136313, not open) RMAN> RMAN> restore database; restore database; Starting restore at 01-MAY-25 using target database control file instead of recovery catalog allocated channel: ORA_DISK_1 channel ORA_DISK_1: SID=2 device type=DISK channel ORA_DISK_1: starting datafile backup set restore channel ORA_DISK_1: specifying datafile(s) to restore from backup set channel ORA_DISK_1: restoring datafile 00001 to /Standby_DB/oradata/STDBY/datafile/o1_mf_system_m33j9fqn_.dbf ... ... ... channel ORA_DISK_1: specifying datafile(s) to restore from backup set channel ORA_DISK_1: restoring datafile 00005 to /Standby_DB/oradata/STDBY/14769E258FBB5FD8E0635A38A8C09D43/datafile/o1_mf_system_m33jb79n_.dbf channel ORA_DISK_1: restoring datafile 00006 to /Standby_DB/oradata/STDBY/14769E258FBB5FD8E0635A38A8C09D43/datafile/o1_mf_sysaux_m33jbbgz_.dbf channel ORA_DISK_1: restoring datafile 00008 to /Standby_DB/oradata/STDBY/14769E258FBB5FD8E0635A38A8C09D43/datafile/o1_mf_undotbs1_m33jbgrs_.dbf channel ORA_DISK_1: reading from backup piece /tmp/STDBY_Backup/DB_DataFiles_ah3objje_337_1_1.bak channel ORA_DISK_1: piece handle=/tmp/STDBY_Backup/DB_DataFiles_ah3objje_337_1_1.bak tag=TAG20250501T074835 channel ORA_DISK_1: restored backup piece 1 channel ORA_DISK_1: restore complete, elapsed time: 00:00:45 Finished restore at 01-MAY-25 RMAN>
Next, I restore the ArchiveLogs that I have in the local backup instead of having to wait for them to be shipped from the Primary during the Recover Phase
RMAN> restore archivelog from time "trunc(sysdate)";
restore archivelog from time "trunc(sysdate)";
Starting restore at 01-MAY-25
using channel ORA_DISK_1
channel ORA_DISK_1: starting archived log restore to default destination
channel ORA_DISK_1: restoring archived log
archived log thread=1 sequence=391
channel ORA_DISK_1: restoring archived log
archived log thread=1 sequence=392
channel ORA_DISK_1: restoring archived log
archived log thread=2 sequence=336
channel ORA_DISK_1: restoring archived log
archived log thread=2 sequence=337
channel ORA_DISK_1: restoring archived log
archived log thread=2 sequence=338
channel ORA_DISK_1: restoring archived log
archived log thread=1 sequence=393
channel ORA_DISK_1: restoring archived log
archived log thread=1 sequence=394
channel ORA_DISK_1: restoring archived log
archived log thread=2 sequence=339
channel ORA_DISK_1: reading from backup piece /tmp/STDBY_Backup/DB_ArchLogs_ad3objeg_333_1_1.bak
channel ORA_DISK_1: piece handle=/tmp/STDBY_Backup/DB_ArchLogs_ad3objeg_333_1_1.bak tag=TAG20250501T074832
channel ORA_DISK_1: restored backup piece 1
channel ORA_DISK_1: restore complete, elapsed time: 00:00:03
Finished restore at 01-MAY-25
RMAN>
RMAN> list archivelog all completed after "trunc(sysdate)";
list archivelog all completed after "trunc(sysdate)";
List of Archived Log Copies for database with db_unique_name STDBY
=====================================================================
Key Thrd Seq S Low Time
------- ---- ------- - ---------
675 1 391 A 27-APR-25
Name: /Standby_DB/FRA/STDBY/archivelog/2025_05_01/o1_mf_1_391_n16fcchs_.arc
667 1 391 A 27-APR-25
Name: /Standby_DB/FRA/STDBY/archivelog/2025_05_01/o1_mf_1_391_n169cng5_.arc
682 1 392 A 01-MAY-25
Name: /Standby_DB/FRA/STDBY/archivelog/2025_05_01/o1_mf_1_392_n16fcbh7_.arc
670 1 392 A 01-MAY-25
Name: /Standby_DB/FRA/STDBY/archivelog/2025_05_01/o1_mf_1_392_n169fh7s_.arc
678 1 393 A 01-MAY-25
Name: /Standby_DB/FRA/STDBY/archivelog/2025_05_01/o1_mf_1_393_n16fcckd_.arc
671 1 393 A 01-MAY-25
Name: /Standby_DB/FRA/STDBY/archivelog/2025_05_01/o1_mf_1_393_n169g77l_.arc
677 1 394 A 01-MAY-25
Name: /Standby_DB/FRA/STDBY/archivelog/2025_05_01/o1_mf_1_394_n16fccjb_.arc
674 1 394 A 01-MAY-25
Name: /Standby_DB/FRA/STDBY/archivelog/2025_05_01/o1_mf_1_394_n169my72_.arc
680 2 336 A 01-MAY-25
Name: /Standby_DB/FRA/STDBY/archivelog/2025_05_01/o1_mf_2_336_n16fccnv_.arc
668 2 336 A 01-MAY-25
Name: /Standby_DB/FRA/STDBY/archivelog/2025_05_01/o1_mf_2_336_n169d0fm_.arc
681 2 337 A 01-MAY-25
Name: /Standby_DB/FRA/STDBY/archivelog/2025_05_01/o1_mf_2_337_n16fcbhy_.arc
669 2 337 A 01-MAY-25
Name: /Standby_DB/FRA/STDBY/archivelog/2025_05_01/o1_mf_2_337_n169fh6j_.arc
679 2 338 A 01-MAY-25
Name: /Standby_DB/FRA/STDBY/archivelog/2025_05_01/o1_mf_2_338_n16fccm6_.arc
672 2 338 A 01-MAY-25
Name: /Standby_DB/FRA/STDBY/archivelog/2025_05_01/o1_mf_2_338_n169g790_.arc
676 2 339 A 01-MAY-25
Name: /Standby_DB/FRA/STDBY/archivelog/2025_05_01/o1_mf_2_339_n16fcchw_.arc
673 2 339 A 01-MAY-25
Name: /Standby_DB/FRA/STDBY/archivelog/2025_05_01/o1_mf_2_339_n169mxfp_.arc
RMAN>
(the output shows duplicate entries if either the ArchiveLogs were already present at the Standby OR the Restore was executed twice)So, I also have the ArchiveLogs now.
I add Standby Logs first (Add for each Thread in the Primary, and at the same size as Online Logs at the Primary)
Now I can begin Recovery of the Standby
I resume Redo Shipping from the Primary
RMAN> exit
exit
sqlRMAN Client Diagnostic Trace file : /u01/app/oracle/diag/clients/user_oracle/host_4144547424_110/trace/ora_5380_139777366395392.trc
Recovery Manager complete.
[oracle@stdby ~]$ sqlplus / as sysdba
SQL> select thread#, group# from v$standby_log;
THREAD# GROUP#
---------- ----------
1 5
2 6
0 7
1 8
1 9
1 10
2 11
2 12
8 rows selected.
SQL> alter database drop standby logfile group 5;
Database altered.
SQL> alter database drop standby logfile group 6;
Database altered.
SQL> alter database drop standby logfile group 7;
Database altered.
SQL> alter database drop standby logfile group 8;
alter database drop standby logfile group 8
*
ERROR at line 1:
ORA-00313: open failed for members of log group 8 of thread 1
ORA-00312: online log 8 thread 1: '/Standby_DB/FRA/STDBY/onlinelog/o1_mf_8_mb6rdbos_.log'
ORA-27037: unable to obtain file status
Linux-x86_64 Error: 2: No such file or directory
Additional information: 7
ORA-00312: online log 8 thread 1: '/Standby_DB/oradata/STDBY/onlinelog/o1_mf_8_mb6rd9h8_.log'
ORA-27037: unable to obtain file status
Linux-x86_64 Error: 2: No such file or directory
Additional information: 7
SQL> alter database drop standby logfile group 9;
Database altered.
SQL> alter database drop standby logfile group 10;
Database altered.
SQL> alter database drop standby logfile group 11;
alter database drop standby logfile group 11
*
ERROR at line 1:
ORA-00313: open failed for members of log group 11 of thread 2
ORA-00312: online log 11 thread 2: '/Standby_DB/FRA/STDBY/onlinelog/o1_mf_11_mb6rf8ob_.log'
ORA-27037: unable to obtain file status
Linux-x86_64 Error: 2: No such file or directory
Additional information: 7
ORA-00312: online log 11 thread 2: '/Standby_DB/oradata/STDBY/onlinelog/o1_mf_11_mb6rf7hs_.log'
ORA-27037: unable to obtain file status
Linux-x86_64 Error: 2: No such file or directory
Additional information: 7
SQL> alter database drop standby logfile group 12;
Database altered.
SQL>
SQL> select thread#, group# from v$standby_log;
THREAD# GROUP#
---------- ----------
1 8
2 11
SQL>
SQL> alter database clear logfile group 8;
Database altered.
SQL> alter database clear logfile group 11;
Database altered.
SQL>
SQL> alter database drop standby logfile group 8;
Database altered.
SQL> alter database drop standby logfile group 11;
Database altered.
SQL> select thread#, group# from v$standby_log;
no rows selected
SQL>
SQL> alter database add standby logfile thread 1 size 512M;
Database altered.
SQL> alter database add standby logfile thread 1 size 512M;
Database altered.
SQL> alter database add standby logfile thread 2 size 512M;
Database altered.
SQL> alter database add standby logfile thread 2 size 512M;
Database altered.
SQL> alter database add standby logfile thread 2 size 512M;
Database altered.
SQL>
SQL> select thread#, group# from v$standby_log order by 1,2;
THREAD# GROUP#
---------- ----------
1 5
1 6
1 7
2 8
2 9
2 10
6 rows selected.
SQL>
I have to clear and then drop and recreate one Standby Log of each Thread that were last being used just before all the files were lost -- so the controlfile expected Group 8 and Group 11 to be present. These were the entries in the alert log for the last set of Recover commands before the storage was lost :2025-05-01T08:10:41.554409+00:00 Recovery of Online Redo Log: Thread 2 Group 11 Seq 343 Reading mem 0 Mem# 0: /Standby_DB/oradata/STDBY/onlinelog/o1_mf_11_mb6rf7hs_.log Mem# 1: /Standby_DB/FRA/STDBY/onlinelog/o1_mf_11_mb6rf8ob_.log 2025-05-01T08:10:41.557828+00:00 ARC1 (PID:1813): Archived Log entry 680 added for B-1164519547.T-1.S-397 LOS:0x0000000000a9f8a3 NXS:0x0000000000a9f8d2 NAB:12 ID 0x46c5be03 LAD:1 2025-05-01T08:10:41.563027+00:00 rfs (PID:1825): Selected LNO:8 for T-1.S-398 dbid 1162136313 branch 1164519547 2025-05-01T08:10:41.642227+00:00 PR00 (PID:1863): Media Recovery Waiting for T-1.S-398 (in transit) 2025-05-01T08:10:41.642508+00:00 Recovery of Online Redo Log: Thread 1 Group 8 Seq 398 Reading mem 0 Mem# 0: /Standby_DB/oradata/STDBY/onlinelog/o1_mf_8_mb6rd9h8_.log Mem# 1: /Standby_DB/FRA/STDBY/onlinelog/o1_mf_8_mb6rdbos_.log 2025-05-01T08:14:02.648081+00:00 Shutting down ORACLE instance (abort) (OS id: 3584)
Now I can begin Recovery of the Standby
SQL> alter database recover managed standby database using current logfile disconnect from session; Database altered. SQL> SQL> shutdown immediate; ORA-01109: database not open Database dismounted. ORACLE instance shut down. SQL> SQL> startup mount; ORACLE instance started. Total System Global Area 2147480256 bytes Fixed Size 9179840 bytes Variable Size 486539264 bytes Database Buffers 1644167168 bytes Redo Buffers 7593984 bytes Database mounted. SQL> alter database recover managed standby database using current logfile disconnect from session; Database altered. SQL> exit
I resume Redo Shipping from the Primary
[oracle@srv1 ~]$ dgmgrl
DGMGRL for Linux: Release 19.0.0.0.0 - Production on Thu May 1 09:11:56 2025
Version 19.25.0.0.0
Copyright (c) 1982, 2019, Oracle and/or its affiliates. All rights reserved.
Welcome to DGMGRL, type "help" for information.
DGMGRL> connect sys
Password:
Connected to "RACDB"
Connected as SYSDBA.
DGMGRL> EDIT DATABASE 'RACDB' SET STATE='TRANSPORT-ON';
Succeeded.
DGMGRL>
DGMGRL> show configuration;
Configuration - racdb_dg
Protection Mode: MaxPerformance
Members:
racdb - Primary database
stdby - Physical standby database
Fast-Start Failover: Disabled
Configuration Status:
SUCCESS (status updated 34 seconds ago)
DGMGRL> show configuration lag;
Configuration - racdb_dg
Protection Mode: MaxPerformance
Members:
racdb - Primary database
stdby - Physical standby database
Transport Lag: 0 seconds (computed 1 second ago)
Apply Lag: 0 seconds (computed 1 second ago)
Fast-Start Failover: Disabled
Configuration Status:
SUCCESS (status updated 37 seconds ago)
DGMGRL>
Note : I have to wait for a few seconds to a few minutes for the SHOW CONFIGURATION and SHOW CONFIGURATION LAG commands to return the correct information. Initially, they may show that there are errors but once Primary and Standby are "talking to each other", these errors would clear.Now my Standby is syncing with the Primary
2025-05-01T09:19:30.530588+00:00 Recovery of Online Redo Log: Thread 2 Group 8 Seq 344 Reading mem 0 Mem# 0: /Standby_DB/oradata/STDBY/onlinelog/o1_mf_8_n16gb9wm_.log Mem# 1: /Standby_DB/FRA/STDBY/onlinelog/o1_mf_8_n16gbb4m_.log 2025-05-01T09:19:30.611573+00:00 rfs (PID:7642): krsr_rfs_atc: Identified database type as 'PHYSICAL': Client is ASYNC (PID:11557) 2025-05-01T09:19:30.623795+00:00 rfs (PID:7642): Selected LNO:5 for T-1.S-399 dbid 1162136313 branch 1164519547 2025-05-01T09:19:30.631133+00:00 PR00 (PID:7486): Media Recovery Waiting for T-1.S-399 (in transit) 2025-05-01T09:19:30.631475+00:00 Recovery of Online Redo Log: Thread 1 Group 5 Seq 399 Reading mem 0 Mem# 0: /Standby_DB/oradata/STDBY/onlinelog/o1_mf_5_n16g90qv_.log Mem# 1: /Standby_DB/FRA/STDBY/onlinelog/o1_mf_5_n16g910n_.log 2025-05-01T09:20:51.263052+00:00 ARC2 (PID:7470): Archived Log entry 691 added for B-1164519547.T-2.S-344 LOS:0x0000000000aa394b NXS:0x0000000000aa3b02 NAB:102 ID 0x46c5be03 LAD:1 2025-05-01T09:20:51.274060+00:00 rfs (PID:7640): Selected LNO:8 for T-2.S-345 dbid 1162136313 branch 1164519547 2025-05-01T09:20:51.285312+00:00 PR00 (PID:7486): Media Recovery Log /Standby_DB/FRA/STDBY/archivelog/2025_05_01/o1_mf_2_344_n16h7m85_.arc PR00 (PID:7486): Media Recovery Waiting for T-2.S-345 (in transit) 2025-05-01T09:20:51.387005+00:00 Recovery of Online Redo Log: Thread 2 Group 8 Seq 345 Reading mem 0 Mem# 0: /Standby_DB/oradata/STDBY/onlinelog/o1_mf_8_n16gb9wm_.log Mem# 1: /Standby_DB/FRA/STDBY/onlinelog/o1_mf_8_n16gbb4m_.log 2025-05-01T09:20:51.433894+00:00 ARC0 (PID:7462): Archived Log entry 692 added for B-1164519547.T-1.S-399 LOS:0x0000000000aa394e NXS:0x0000000000aa3b06 NAB:265 ID 0x46c5be03 LAD:1 2025-05-01T09:20:51.445431+00:00 rfs (PID:7642): Selected LNO:5 for T-1.S-400 dbid 1162136313 branch 1164519547 2025-05-01T09:20:51.514317+00:00 PR00 (PID:7486): Media Recovery Waiting for T-1.S-400 (in transit) 2025-05-01T09:20:51.514664+00:00 Recovery of Online Redo Log: Thread 1 Group 5 Seq 400 Reading mem 0 Mem# 0: /Standby_DB/oradata/STDBY/onlinelog/o1_mf_5_n16g90qv_.log Mem# 1: /Standby_DB/FRA/STDBY/onlinelog/o1_mf_5_n16g910n_.logI see that the SEQ# have already advanced to 399 and 345 for Thread 1 and 2 respectively.
Categories: DBA Blogs
Flashback a Pluggable Database in RAC with Data Guard
I have published a new video Flashback PDB in RAC with DG.
Here are some important considerations / commands when you want to use Flashback :
1. Ensure that you have FLASHBACK_ON in the Database (at both Primary and Standby). If you don't have FLASHBACK_ON, ensure that you create the RESTORE POINT WITH GUARANTEE FLASHBACK DATABASE at both Primary and Standby. (In the latter case, the Flashback SCN / Point In Time of the Standby must be lower than that of the Primary).
3. Monitor the FRA (Recovery Area) (V$FLASH_RECOVERY_AREA_USAGE) and Oldest Flashback Time (in V$FLASHBACK_DATABASE_LOG). If necessary, increase DB_FLASHBACK_RETENTION_TARGET and DB_RECOVERY_FILE_DEST_SIZE to ensure that you don't run out of space for the Flashback Logs !
2. If you have used dgmgrl -- i.e. Data Guard Broker Configuration, all commands to Stop Redo Shipping / Resume Redo Shipping, Stop Redo Apply / Resume Redo Apply must be issued through dgmgrl. Do not use SQL commands.
3. At the Standby the Flashback command uses the "STANDBY" clause to identify that you are doing a Flashback for a Standby.
Some older Blog Posts on FLASHBACK DATABASE are at Blog Series on Flashback Database.
Categories: DBA Blogs
Video on Client Connectivity options for RAC
Last month, I had posted a new Video on Client Connectivity options in RAC.
It shows different methods of Client (ie. Applications as well !) -- not just using SCAN Name in an Oracle RAC Cluster
On Client-Side Load Balancing see the sections "Generic Database Clients" and "Client-Side Load Balancing" in the Chapter on Workload Management athttps://docs.oracle.com/en/database/oracle/oracle-database/19/racad/workload-management-with-dynamic-database-services.html
A few blog posts about services in RAC :
https://hemantoracledba.blogspot.com/2014/07/rac-commands-1-viewing-configuration.html
https://hemantoracledba.blogspot.com/2014/07/rac-commands-2-updating-configuration.html
https://hemantoracledba.blogspot.com/2017/04/12cr1-rac-posts-9-adding-service-to-pdb.html
https://hemantoracledba.blogspot.com/2024/02/adding-pdb-and-service-to-rac-database.html
Categories: DBA Blogs
Domains in 23ai Schema Development
I had heard of Data Use Case Domains in 23ai. However, the New Features nd Database Concepts documentation didn't provide enough examples for me to build on.
However, this blog post by Ulrike Schwinn (which was shared by @thatjeffsmith on X) helped me explore domains.
In this demo, I am using the Pre-Seeded Domains. However, you can see the example posted by Ulrike Schwimm or even read in the Database Concepts documentation to help build your own custom Domains.
A Data Use Case Domain is like defining a Custom DataType such that only valid values are permitted. The Domain name can be a self-identifier (just as "DATE" or "NUMBER" identifies the type of data being stored).
Here is my demonstration (I also use the Annotations feature -- the Data Use Case Domains documentation links above also lead to this feature)
SQL> set pages600 linesize 132
SQL> col contact_person format a32
SQL> col contact_email format a24
SQL>
SQL> drop table forex_rates_contacts;
Table dropped.
SQL>
SQL>
SQL> create table forex_rates_contacts
2 (
3 country_iso_code varchar2(3) domain country_code_d, -- preseeded SYS domain
4 currency_code varchar2(3) domain currency_code_d, -- preseeded SYS domain
5 contact_person varchar2(128),
6 contact_email varchar2(4000) domain email_d -- preseed SYS domain
7 )
8 annotations (display 'Forex Contact Persons')
9 /
Table created.
SQL>
SQL> desc forex_rates_contacts
Name Null? Type
------------------------------------------------------------------------ -------- -------------------------------------------------
COUNTRY_ISO_CODE VARCHAR2(3) SYS.COUNTRY_CODE_D
CURRENCY_CODE VARCHAR2(3) SYS.CURRENCY_CODE_D
CONTACT_PERSON VARCHAR2(128)
CONTACT_EMAIL VARCHAR2(4000) SYS.EMAIL_D
SQL>
SQL>
SQL> set long 1000
SQL> set longc 1000
SQL> set serveroutput on
SQL>
SQL> rem FROM clause is no longer required in 23ai
SQL> select dbms_metadata.get_ddl('TABLE','FOREX_RATES_CONTACTS','HEMANT');
DBMS_METADATA.GET_DDL('TABLE','FOREX_RATES_CONTACTS','HEMANT')
------------------------------------------------------------------------------------------------------------------------------------
CREATE TABLE "HEMANT"."FOREX_RATES_CONTACTS"
( "COUNTRY_ISO_CODE" VARCHAR2(3) DOMAIN "SYS"."COUNTRY_CODE_D",
"CURRENCY_CODE" VARCHAR2(3) DOMAIN "SYS"."CURRENCY_CODE_D",
"CONTACT_PERSON" VARCHAR2(128),
"CONTACT_EMAIL" VARCHAR2(4000) DOMAIN "SYS"."EMAIL_D"
) SEGMENT CREATION DEFERRED
PCTFREE 10 PCTUSED 40 INITRANS 1 MAXTRANS 255
NOCOMPRESS LOGGING
TABLESPACE "USERS"
ANNOTATIONS("DISPLAY" 'Forex Contact Persons')
SQL>
SQL>
SQL>
SQL> rem MULTI-ROW Insert
SQL> insert into forex_rates_contacts
2 values
3 ('US','USD','Mr Unknown','unknown@nowhere.gov'),
4 ('IN','INR','Someone at RBI','someone@rbi.gov.in')
5 /
2 rows created.
SQL>
SQL> commit;
Commit complete.
SQL>
SQL> select * from forex_rates_contacts
2 order by country_iso_code
3 /
COU CUR CONTACT_PERSON CONTACT_EMAIL
--- --- -------------------------------- ------------------------
IN INR Someone at RBI someone@rbi.gov.in
US USD Mr Unknown unknown@nowhere.gov
SQL>
SQL> -- Note that the country_code_d and currency_code_d do not check validity against really ISO codes
SQL> -- thus, it does not disallow "ZZ" and "ZZZ"
SQL> insert into forex_rates_contacts
2 values
3 ('ZZ','ZZZ','Mr Unknown','unknown@nowhere.zz')
4 /
1 row created.
SQL>
SQL> select * from forex_rates_contacts
2 order by country_iso_code
3 /
COU CUR CONTACT_PERSON CONTACT_EMAIL
--- --- -------------------------------- ------------------------
IN INR Someone at RBI someone@rbi.gov.in
US USD Mr Unknown unknown@nowhere.gov
ZZ ZZZ Mr Unknown unknown@nowhere.zz
SQL>
SQL> commit;
Commit complete.
SQL>
SQL> -- But the rules for email validation are encoded
SQL> insert into forex_rates_contacts
2 values
3 ('UK','GBP','Mr Someone','someone@x')
4 /
insert into forex_rates_contacts
*
ERROR at line 1:
ORA-11534: check constraint (HEMANT.SYS_C0013464) involving column CONTACT_EMAIL due to domain constraint SYS.SYS_DOMAIN_C0030 of
domain SYS.EMAIL_D violated
Help: https://docs.oracle.com/error-help/db/ora-11534/
SQL>
SQL> select * from forex_rates_contacts
2 order by country_iso_code
3 /
COU CUR CONTACT_PERSON CONTACT_EMAIL
--- --- -------------------------------- ------------------------
IN INR Someone at RBI someone@rbi.gov.in
US USD Mr Unknown unknown@nowhere.gov
ZZ ZZZ Mr Unknown unknown@nowhere.zz
SQL>
SQL> spool off
I haven't added my own custom Domains but used the PreSeeded domains for Country, Currency and Email. Look at "10.1.12 Built-In Use Case Domains" in the documentation.
Categories: DBA Blogs
23ai New Feature : Partition HIGH_VALUE in JSON format
A quick demonstration of the new HIGH_VALUE_JSON column in the USER_TAB_PARTITIONS view in 23ai :
[oracle@localhost Hemant]$ sqlplus hemant/hemant@freepdb1
SQL*Plus: Release 23.0.0.0.0 - for Oracle Cloud and Engineered Systems on Sun Jan 26 10:07:09 2025
Version 23.6.0.24.10
Copyright (c) 1982, 2024, Oracle. All rights reserved.
Last Successful login time: Sun Jan 26 2025 10:05:18 +00:00
Connected to:
Oracle Database 23ai Free Release 23.0.0.0.0 - Develop, Learn, and Run for Free
Version 23.6.0.24.10
SQL> @demo_part_high_value.sql
SQL> set pages600 linesize 132
SQL> set long 10000
SQL>
SQL> spool demo_part_high_value
SQL>
SQL> -- 23ai has two new columns in the USER_TAB_PARTTIIONS view
SQL> -- HIGH_VALUE_CLOB and HIGH_VALUE_JSON
SQL> --- unlike HIGH_VALUE which is a LONG, these two can be used programmatically
SQL> -- here I show HIGH_VALUE_JSON along with the HIGH_VALUE
SQL>
SQL> set pages600 linesize 132
SQL> set long 10000
SQL> col partition_name format a8 hea 'P_Name'
SQL> col high_value format a56 trunc hea 'High_Value_LONG' trunc
SQL> col high_value_json format a48 hea 'High_Value_JSON'
SQL>
SQL>
SQL> drop table hkc_test_intvl;
Table dropped.
SQL>
SQL> create table hkc_test_intvl
2 (date_column date,
3 data_column varchar2(50))
4 partition by range (date_column)
5 interval (numtoyminterval(1,'MONTH'))
6 (partition P_1 values less than (to_date('01-FEB-2024','DD-MON-YYYY')))
7 /
Table created.
SQL>
SQL>
SQL> insert into hkc_Test_intvl
2 values (to_date('15-AUG-2024','DD-MON-YYYY'), 'August Row')
3 /
1 row created.
SQL>
SQL>
SQL> insert into hkc_test_intvl
2 values (to_date('15-OCT-2024','DD-MON-YYYY'),'October Row')
3 /
1 row created.
SQL>
SQL> insert into hkc_test_intvl
2 values (to_date('15-DEC-2024','DD-MON-YYYY'),'December Row')
3 /
1 row created.
SQL>
SQL> select partition_name, high_value, high_value_json
2 from user_tab_partitions
3 where table_name = 'HKC_TEST_INTVL'
4 /
P_Name High_Value_LONG High_Value_JSON
-------- -------------------------------------------------------- ------------------------------------------------
P_1 TO_DATE(' 2024-02-01 00:00:00', 'SYYYY-MM-DD HH24:MI:SS' {"high_value":"2024-02-01T00:00:00"}
SYS_P447 TO_DATE(' 2024-09-01 00:00:00', 'SYYYY-MM-DD HH24:MI:SS' {"high_value":"2024-09-01T00:00:00"}
SYS_P448 TO_DATE(' 2024-11-01 00:00:00', 'SYYYY-MM-DD HH24:MI:SS' {"high_value":"2024-11-01T00:00:00"}
SYS_P449 TO_DATE(' 2025-01-01 00:00:00', 'SYYYY-MM-DD HH24:MI:SS' {"high_value":"2025-01-01T00:00:00"}
SQL>
SQL>
SQL> spool off
Earlier, HIGH_VALUE was presented as a LONG.
23ai adds two columns to the USER_TAB_PARTITIONS data dictionary view :
HIGH_VALUE_CLOB
and
HIGH_VALUE_JSON
These make it easier to query the data dictionary, for example, for Partition Life Cycle management.
Categories: DBA Blogs
Querying the Alert log in RAC
Although v$diag_alert_ext works for a single instance, there is no corresponding gv$ view for RAC.
However, the gv$ function can be used to execute a cursor across all instances. Here I query for the alert log in the two nodes srv1 and srv2 and order the results by timestamp to capture messages in the last 15 minutes : Note all the activity that happens when I CLOSE and later OPEN a PDB in one node, resulting in the other node also responding to maintain Global Resources.
SQL> l 1 select * from table(gv$(cursor 2 (select originating_timestamp, host_id, con_id, message_text 3 from v$diag_alert_ext 4 where originating_timestamp > sysdate - 0.25/24 -- time filter 5 and message_text like '%' -- message filter 6 ) 7 ) 8 ) 9* order by 1,2,3 SQL> / ORIGINATING_TIMESTAMP --------------------------------------------------------------------------- HOST_ID CON_ID ------------------------------------------------------------------- ---------- MESSAGE_TEXT ------------------------------------------------------------------------------------------------------------------------------------ 07-JAN-25 02.23.37.941000000 PM +00:00 srv2 1 Thread 2 cannot allocate new log, sequence 278 07-JAN-25 02.23.37.941000000 PM +00:00 srv2 1 Checkpoint not complete 07-JAN-25 02.23.37.941000000 PM +00:00 srv2 1 Current log# 3 seq# 277 mem# 0: +DATA/RACDB/ONLINELOG/group_3.270.1164520171 07-JAN-25 02.23.37.941000000 PM +00:00 srv2 1 Current log# 3 seq# 277 mem# 1: +FRA/RACDB/ONLINELOG/group_3.259.1164520171 07-JAN-25 02.23.38.255000000 PM +00:00 srv1 1 Thread 1 cannot allocate new log, sequence 322 07-JAN-25 02.23.38.255000000 PM +00:00 srv1 1 Current log# 1 seq# 321 mem# 1: +FRA/RACDB/ONLINELOG/group_1.257.1164519549 07-JAN-25 02.23.38.255000000 PM +00:00 srv1 1 Current log# 1 seq# 321 mem# 0: +DATA/RACDB/ONLINELOG/group_1.263.1164519549 07-JAN-25 02.23.38.255000000 PM +00:00 srv1 1 Checkpoint not complete 07-JAN-25 02.23.40.951000000 PM +00:00 srv2 1 Thread 2 advanced to log sequence 278 (LGWR switch), current SCN: 10841502 07-JAN-25 02.23.40.951000000 PM +00:00 srv2 1 Current log# 4 seq# 278 mem# 0: +DATA/RACDB/ONLINELOG/group_4.271.1164520171 07-JAN-25 02.23.40.951000000 PM +00:00 srv2 1 Current log# 4 seq# 278 mem# 1: +FRA/RACDB/ONLINELOG/group_4.260.1164520173 07-JAN-25 02.23.40.976000000 PM +00:00 srv2 1 Deleted Oracle managed file +FRA/RACDB/ARCHIVELOG/2024_11_02/thread_1_seq_240.500.1183975081 07-JAN-25 02.23.40.977000000 PM +00:00 srv2 1 ARC2 (PID:17940): Archived Log entry 1023 added for B-1164519547.T-2.S-277 LOS:0x0000000000a568cc NXS:0x0000000000a56d9e NAB:372 ID 0x46c5be03 LAD:1 07-JAN-25 02.23.41.048000000 PM +00:00 srv1 1 Thread 1 advanced to log sequence 322 (LGWR switch), current SCN: 10841505 07-JAN-25 02.23.41.048000000 PM +00:00 srv1 1 Current log# 2 seq# 322 mem# 1: +FRA/RACDB/ONLINELOG/group_2.258.1164519549 07-JAN-25 02.23.41.048000000 PM +00:00 srv1 1 Current log# 2 seq# 322 mem# 0: +DATA/RACDB/ONLINELOG/group_2.262.1164519549 07-JAN-25 02.23.41.117000000 PM +00:00 srv2 1 Deleted Oracle managed file +FRA/RACDB/ARCHIVELOG/2024_11_02/thread_2_seq_221.499.1183975181 07-JAN-25 02.23.41.138000000 PM +00:00 srv1 1 Deleted Oracle managed file +FRA/RACDB/ARCHIVELOG/2024_11_02/thread_2_seq_222.498.1183975205 07-JAN-25 02.23.41.139000000 PM +00:00 srv1 1 NET (PID:15641): Archived Log entry 1025 added for B-1164519547.T-1.S-321 LOS:0x0000000000a568c9 NXS:0x0000000000a56da1 NAB:369 ID 0x46c5be03 LAD:1 07-JAN-25 02.23.41.209000000 PM +00:00 srv1 1 Deleted Oracle managed file +FRA/RACDB/ARCHIVELOG/2024_11_02/thread_1_seq_241.497.1183975551 07-JAN-25 02.27.41.986000000 PM +00:00 srv1 1 alter pluggable database pdb1 close 07-JAN-25 02.27.41.997000000 PM +00:00 srv1 3 Pluggable database PDB1 closing 07-JAN-25 02.27.42.004000000 PM +00:00 srv1 3 Increasing priority of 2 RS 07-JAN-25 02.27.42.011000000 PM +00:00 srv1 3 JIT: pid 19878 requesting stop 07-JAN-25 02.27.42.044000000 PM +00:00 srv1 3 Stopped service mypdb 07-JAN-25 02.27.42.208000000 PM +00:00 srv1 3 Closing sequence subsystem (3300983922). 07-JAN-25 02.27.42.332000000 PM +00:00 srv1 3 Buffer Cache flush started: 3 07-JAN-25 02.27.42.345000000 PM +00:00 srv1 3 Buffer Cache flush finished: 3 07-JAN-25 02.27.42.347000000 PM +00:00 srv2 1 Increasing priority of 2 RS 07-JAN-25 02.27.42.350000000 PM +00:00 srv1 3 queued detach DA request 0x934eafc8 for pdb 3, ospid 19878 07-JAN-25 02.27.42.351000000 PM +00:00 srv1 1 Domain Action Reconfiguration started (domid 3, new da inc 3, cluster inc 8) 07-JAN-25 02.27.42.351000000 PM +00:00 srv1 1 Instance 1 is detaching from domain 3 (lazy abort? 0, recovery member? 0) 07-JAN-25 02.27.42.352000000 PM +00:00 srv1 1 Global Resource Directory partially frozen for domain action 07-JAN-25 02.27.42.352000000 PM +00:00 srv1 1 * domain detach - domain 3 valid ? 1 07-JAN-25 02.27.42.430000000 PM +00:00 srv2 1 Domain Action Reconfiguration started (domid 3, new da inc 3, cluster inc 8) 07-JAN-25 02.27.42.430000000 PM +00:00 srv2 1 Instance 1 is detaching from domain 3 (lazy abort? 0, recovery member? 0) 07-JAN-25 02.27.42.430000000 PM +00:00 srv2 1 Global Resource Directory partially frozen for domain action 07-JAN-25 02.27.42.430000000 PM +00:00 srv2 1 * domain detach - domain 3 valid ? 1 07-JAN-25 02.27.42.432000000 PM +00:00 srv2 1 Non-local Process blocks cleaned out 07-JAN-25 02.27.42.434000000 PM +00:00 srv2 1 Set master node info 07-JAN-25 02.27.42.435000000 PM +00:00 srv2 1 Dwn-cvts replayed, VALBLKs dubious 07-JAN-25 02.27.42.435000000 PM +00:00 srv2 1 All grantable enqueues granted 07-JAN-25 02.27.42.437000000 PM +00:00 srv1 1 Non-local Process blocks cleaned out 07-JAN-25 02.27.42.438000000 PM +00:00 srv1 1 Set master node info 07-JAN-25 02.27.42.439000000 PM +00:00 srv1 1 Dwn-cvts replayed, VALBLKs dubious 07-JAN-25 02.27.42.440000000 PM +00:00 srv1 1 All grantable enqueues granted 07-JAN-25 02.27.42.440000000 PM +00:00 srv2 1 Domain Action Reconfiguration complete (total time 0.0 secs) 07-JAN-25 02.27.42.440000000 PM +00:00 srv2 1 Decreasing priority of 2 RS 07-JAN-25 02.27.42.444000000 PM +00:00 srv1 1 freeing the fusion rht of pdb 3 07-JAN-25 02.27.42.445000000 PM +00:00 srv1 1 freeing the pdb enqueue rht 07-JAN-25 02.27.42.445000000 PM +00:00 srv1 1 Decreasing priority of 2 RS 07-JAN-25 02.27.42.445000000 PM +00:00 srv1 1 Domain Action Reconfiguration complete (total time 0.1 secs) 07-JAN-25 02.27.42.542000000 PM +00:00 srv1 1 Pluggable database PDB1 closed 07-JAN-25 02.27.42.571000000 PM +00:00 srv1 1 Completed: alter pluggable database pdb1 close 07-JAN-25 02.28.10.713000000 PM +00:00 srv1 1 alter pluggable database pdb1 open 07-JAN-25 02.28.10.715000000 PM +00:00 srv1 3 Pluggable database PDB1 opening in read write 07-JAN-25 02.28.10.892000000 PM +00:00 srv1 3 Increasing priority of 2 RS 07-JAN-25 02.28.10.892000000 PM +00:00 srv1 3 Autotune of undo retention is turned on. 07-JAN-25 02.28.10.892000000 PM +00:00 srv1 3 SUPLOG: Initialize PDB SUPLOG SGA, old value 0x0, new value 0x18 07-JAN-25 02.28.10.929000000 PM +00:00 srv1 3 queued attach DA request 0x934eaf60 for pdb 3, ospid 19878 07-JAN-25 02.28.10.929000000 PM +00:00 srv2 1 Increasing priority of 2 RS 07-JAN-25 02.28.10.933000000 PM +00:00 srv1 1 Domain Action Reconfiguration started (domid 3, new da inc 4, cluster inc 8) 07-JAN-25 02.28.10.933000000 PM +00:00 srv1 1 Global Resource Directory partially frozen for domain action 07-JAN-25 02.28.10.933000000 PM +00:00 srv1 1 Instance 1 is attaching to domain 3 07-JAN-25 02.28.10.940000000 PM +00:00 srv2 1 Domain Action Reconfiguration started (domid 3, new da inc 4, cluster inc 8) 07-JAN-25 02.28.10.940000000 PM +00:00 srv2 1 Instance 1 is attaching to domain 3 07-JAN-25 02.28.10.941000000 PM +00:00 srv2 1 Global Resource Directory partially frozen for domain action 07-JAN-25 02.28.10.943000000 PM +00:00 srv2 1 Non-local Process blocks cleaned out 07-JAN-25 02.28.10.946000000 PM +00:00 srv2 1 Set master node info 07-JAN-25 02.28.10.947000000 PM +00:00 srv1 1 Non-local Process blocks cleaned out 07-JAN-25 02.28.10.947000000 PM +00:00 srv2 1 Dwn-cvts replayed, VALBLKs dubious 07-JAN-25 02.28.10.948000000 PM +00:00 srv1 1 Set master node info 07-JAN-25 02.28.10.949000000 PM +00:00 srv2 1 All grantable enqueues granted 07-JAN-25 02.28.10.952000000 PM +00:00 srv1 1 Dwn-cvts replayed, VALBLKs dubious 07-JAN-25 02.28.10.953000000 PM +00:00 srv1 1 All grantable enqueues granted 07-JAN-25 02.28.11.034000000 PM +00:00 srv2 1 Domain Action Reconfiguration complete (total time 0.1 secs) 07-JAN-25 02.28.11.034000000 PM +00:00 srv2 1 Decreasing priority of 2 RS 07-JAN-25 02.28.11.038000000 PM +00:00 srv1 1 Domain Action Reconfiguration complete (total time 0.1 secs) 07-JAN-25 02.28.11.038000000 PM +00:00 srv1 1 Decreasing priority of 2 RS 07-JAN-25 02.28.11.135000000 PM +00:00 srv1 3 Endian type of dictionary set to little 07-JAN-25 02.28.11.213000000 PM +00:00 srv1 3 Undo initialization recovery: err:0 start: 3329988 end: 3329989 diff: 1 ms (0.0 seconds) 07-JAN-25 02.28.11.352000000 PM +00:00 srv1 3 [19878] Successfully onlined Undo Tablespace 2. 07-JAN-25 02.28.11.352000000 PM +00:00 srv1 3 Undo initialization online undo segments: err:0 start: 3329989 end: 3330129 diff: 140 ms (0.1 seconds) 07-JAN-25 02.28.11.357000000 PM +00:00 srv1 3 Undo initialization finished serial:0 start:3329988 end:3330134 diff:146 ms (0.1 seconds) 07-JAN-25 02.28.11.361000000 PM +00:00 srv1 3 Database Characterset for PDB1 is AL32UTF8 07-JAN-25 02.28.11.627000000 PM +00:00 srv1 3 SUPLOG: Set PDB SUPLOG SGA at PDB OPEN, old 0x18, new 0x0 (no suplog) 07-JAN-25 02.28.11.891000000 PM +00:00 srv1 3 Started service mypdb/mypdb/mypdb 07-JAN-25 02.28.11.925000000 PM +00:00 srv1 3 Opening pdb with no Resource Manager plan active 07-JAN-25 02.28.12.097000000 PM +00:00 srv1 3 joxcsys_required_dirobj_exists: directory object exists with required path /u02/app/oracle/product/19.0.0/dbhome_1/javavm/admin/, pi d 19878 cid 3 07-JAN-25 02.28.12.118000000 PM +00:00 srv1 1 Pluggable database PDB1 opened read write 07-JAN-25 02.28.12.122000000 PM +00:00 srv1 1 Completed: alter pluggable database pdb1 open 07-JAN-25 02.33.26.501000000 PM +00:00 srv1 1 Control autobackup written to DISK device 07-JAN-25 02.33.26.502000000 PM +00:00 srv1 1 handle '+FRA/RACDB/AUTOBACKUP/2025_01_07/s_1189780406.497.1189780407' 93 rows selected. SQL>At 07-JAN-25 02.27.41.986000000 PM +00:00 : I issued a command to close PDB1 (CON_ID=3) on host srv1
You can also see the "Stopped service mypdb" message on srv1 at 07-JAN-25 02.27.42
Host srv2 started writing it's messages at 07-JAN-25 02.27.42.347000000 PM +00:00 from which you can see Domain Action Reconfiguration (07-JAN-25 02.27.42.351000000 PM +00:00), Global Resource Directory partially frozen (07-JAN-25 02.27.42.430000000 PM +00:00)/
Finally, srv1 logged "Completed: alter pluggable database pdb1 close" at 07-JAN-25 02.27.42.571000000 PM +00:00 (under CON_ID=1).
When I issued the "alter pluggable database pdb1 open" on srv1 at 07-JAN-25 02.28.10.713000000 PM +00:00, Domain Actions and Global Resource Directory actions were executed again on srv2
Finally, srv1 logged "Completed: alter pluggable database pdb1 open" at 07-JAN-25 02.28.12.122000000 PM +00:00
So, it is obvious that closing and opening a PDB in RAC also results in a number of steps to maintain consistency (Resources etc) across the instances.
Categories: DBA Blogs
3million PageViews, 303thousand VideoViews
This blog, begun in December 2006, has now hit a cumulative count of 3million PageViews.
This Chart shows counts from the year 2011 :
My YouTube Channel, begun in January 2014, has hit a cumulative count of 303thousand views :
A Big Thank You to all the Viewers an Subscribers.
Categories: DBA Blogs
DataPump with CheckSum in 21c and above
Oracle introduced a CheckSum parameter in 21c. Here is a demo in 23.6.
First I run the datapump export without the CheckSum:
[oracle@localhost ~]$ expdp hemant/hemant@freepdb1 schemas=HEMANT dumpfile=HEMANT Export: Release 23.0.0.0.0 - Limited Availability on Sat Dec 28 12:31:26 2024 Version 23.6.0.24.10 Copyright (c) 1982, 2024, Oracle and/or its affiliates. All rights reserved. Connected to: Oracle Database 23ai Free Release 23.0.0.0.0 - Develop, Learn, and Run for Free Starting "HEMANT"."SYS_EXPORT_SCHEMA_01": hemant/********@freepdb1 schemas=HEMANT dumpfile=HEMANT Processing object type SCHEMA_EXPORT/TABLE/TABLE_DATA Processing object type SCHEMA_EXPORT/TABLE/INDEX/STATISTICS/INDEX_STATISTICS Processing object type SCHEMA_EXPORT/TABLE/STATISTICS/TABLE_STATISTICS Processing object type SCHEMA_EXPORT/USER Processing object type SCHEMA_EXPORT/SYSTEM_GRANT Processing object type SCHEMA_EXPORT/ROLE_GRANT Processing object type SCHEMA_EXPORT/DEFAULT_ROLE Processing object type SCHEMA_EXPORT/PRE_SCHEMA/PROCACT_SCHEMA/LOGREP Processing object type SCHEMA_EXPORT/TABLE/TABLE Processing object type SCHEMA_EXPORT/TABLE/COMMENT Processing object type SCHEMA_EXPORT/TABLE/INDEX/INDEX . . exported "HEMANT"."MY_LOBS" 7.9 MB 75929 rows Master table "HEMANT"."SYS_EXPORT_SCHEMA_01" successfully loaded/unloaded ****************************************************************************** Dump file set for HEMANT.SYS_EXPORT_SCHEMA_01 is: /opt/oracle/admin/FREE/dpdump/2917EBB8705B3129E0630100007F3D2B/HEMANT.dmp Job "HEMANT"."SYS_EXPORT_SCHEMA_01" successfully completed at Sat Dec 28 12:32:06 2024 elapsed 0 00:00:38 [oracle@localhost ~]$
Now this is an export WITH the CheckSum (after verifying that COMPATIBLE is 20.0 or higher) by specifying CHECKSUM=YES :
[oracle@localhost ~]$ sqlplus hemant/hemant@freepdb1 SQL*Plus: Release 23.0.0.0.0 - for Oracle Cloud and Engineered Systems on Sat Dec 28 12:35:20 2024 Version 23.6.0.24.10 Copyright (c) 1982, 2024, Oracle. All rights reserved. Last Successful login time: Sat Dec 28 2024 12:31:26 +00:00 Connected to: Oracle Database 23ai Free Release 23.0.0.0.0 - Develop, Learn, and Run for Free Version 23.6.0.24.10 SQL> show parameter compatible NAME TYPE VALUE ------------------------------------ ----------- ------------------------------ compatible string 23.6.0 noncdb_compatible boolean FALSE SQL> quit Disconnected from Oracle Database 23ai Free Release 23.0.0.0.0 - Develop, Learn, and Run for Free Version 23.6.0.24.10 [oracle@localhost ~]$ expdp hemant/hemant@freepdb1 schemas=HEMANT dumpfile=HEMANT_With_CheckSum checksum=YES Export: Release 23.0.0.0.0 - Limited Availability on Sat Dec 28 12:35:55 2024 Version 23.6.0.24.10 Copyright (c) 1982, 2024, Oracle and/or its affiliates. All rights reserved. Connected to: Oracle Database 23ai Free Release 23.0.0.0.0 - Develop, Learn, and Run for Free Starting "HEMANT"."SYS_EXPORT_SCHEMA_01": hemant/********@freepdb1 schemas=HEMANT dumpfile=HEMANT_With_CheckSum checksum=YES Processing object type SCHEMA_EXPORT/TABLE/TABLE_DATA Processing object type SCHEMA_EXPORT/TABLE/INDEX/STATISTICS/INDEX_STATISTICS Processing object type SCHEMA_EXPORT/TABLE/STATISTICS/TABLE_STATISTICS Processing object type SCHEMA_EXPORT/USER Processing object type SCHEMA_EXPORT/SYSTEM_GRANT Processing object type SCHEMA_EXPORT/ROLE_GRANT Processing object type SCHEMA_EXPORT/DEFAULT_ROLE Processing object type SCHEMA_EXPORT/PRE_SCHEMA/PROCACT_SCHEMA/LOGREP Processing object type SCHEMA_EXPORT/TABLE/TABLE Processing object type SCHEMA_EXPORT/TABLE/COMMENT Processing object type SCHEMA_EXPORT/TABLE/INDEX/INDEX . . exported "HEMANT"."MY_LOBS" 7.9 MB 75929 rows Master table "HEMANT"."SYS_EXPORT_SCHEMA_01" successfully loaded/unloaded Generating checksums for dump file set ****************************************************************************** Dump file set for HEMANT.SYS_EXPORT_SCHEMA_01 is: /opt/oracle/admin/FREE/dpdump/2917EBB8705B3129E0630100007F3D2B/HEMANT_With_CheckSum.dmp Job "HEMANT"."SYS_EXPORT_SCHEMA_01" successfully completed at Sat Dec 28 12:36:33 2024 elapsed 0 00:00:36 [oracle@localhost ~]$
After I transfer the dumpfile to another server, I verify the CheckSum with VERIFY_ONLY=YES:
[oracle@localhost ~]$ sqlplus / as sysdba SQL*Plus: Release 23.0.0.0.0 - for Oracle Cloud and Engineered Systems on Sat Dec 28 12:40:54 2024 Version 23.6.0.24.10 Copyright (c) 1982, 2024, Oracle. All rights reserved. Connected to: Oracle Database 23ai Free Release 23.0.0.0.0 - Develop, Learn, and Run for Free Version 23.6.0.24.10 SQL> create directory impdp_check as '/tmp'; Directory created. SQL> quit Disconnected from Oracle Database 23ai Free Release 23.0.0.0.0 - Develop, Learn, and Run for Free Version 23.6.0.24.10 [oracle@localhost ~]$ impdp directory=impdp_check dumpfile=HEMANT_With_CheckSum.dmp verify_only=YES Import: Release 23.0.0.0.0 - Limited Availability on Sat Dec 28 12:42:28 2024 Version 23.6.0.24.10 Copyright (c) 1982, 2024, Oracle and/or its affiliates. All rights reserved. Username: / as sysdba Connected to: Oracle Database 23ai Free Release 23.0.0.0.0 - Develop, Learn, and Run for Free Warning: Oracle Data Pump operations are not typically needed when connected to the root or seed of a container database. Verifying dump file checksums Master table "SYS"."SYS_IMPORT_FULL_01" successfully loaded/unloaded dump file set is complete verified checksum for dump file "/tmp/HEMANT_With_CheckSum.dmp" dump file set is consistent Job "SYS"."SYS_IMPORT_FULL_01" successfully completed at Sat Dec 28 12:42:39 2024 elapsed 0 00:00:05 [oracle@localhost ~]$ [oracle@localhost ~]$ cd /tmp [oracle@localhost tmp]$ ls -l import.log -rw-r--r--. 1 oracle oinstall 600 Dec 28 12:42 import.log [oracle@localhost tmp]$ cat import.log ;;; Import: Release 23.0.0.0.0 - Limited Availability on Sat Dec 28 12:42:28 2024 Version 23.6.0.24.10 Copyright (c) 1982, 2024, Oracle and/or its affiliates. All rights reserved. ;;; Connected to: Oracle Database 23ai Free Release 23.0.0.0.0 - Develop, Learn, and Run for Free Verifying dump file checksums Master table "SYS"."SYS_IMPORT_FULL_01" successfully loaded/unloaded dump file set is complete verified checksum for dump file "/tmp/HEMANT_With_CheckSum.dmp" dump file set is consistent Job "SYS"."SYS_IMPORT_FULL_01" successfully completed at Sat Dec 28 12:42:39 2024 elapsed 0 00:00:05 [oracle@localhost tmp]$
The VERIFY_ONLY parameter verifies the file without actually importing the dump file.
The default CheckSum algorithm is SHA256.
You can override this by specifying CHECKSUM_ALGORITHM set to either of CRC32, SHA256, SHA384 or SHA512.
Categories: DBA Blogs
The GROUP BY column_position enhancement in 23ai
Oracle 23ai allows specifying a Column Position (or Alias) in the GROUP BY clause.
For backward compatibility, the "group_by_position_enabled" parameter is a new feature that defaults to FALSE.
SQL> show parameter group_by_position_enabled NAME TYPE VALUE ------------------------------------ ----------- ------------------------------ group_by_position_enabled boolean FALSE SQL> alter session set group_by_position_enabled=TRUE; Session altered. SQL> SQL> select p.prod_name, t.day_name, sum(s.amount_sold) 2 from sh.products p, sh.times t, sh.sales s 3 where p.prod_id=s.prod_id 4 and t.time_id=s.time_id 5 and t.calendar_month_name = 'January' 6 group by 1, 2 7 order by 1, 2 8 / PROD_NAME DAY_NAME SUM(S.AMOUNT_SOLD) -------------------------------------------------- --------- ------------------ 11" Youth Field Master Glove Friday 4635.73 11" Youth Field Master Glove Monday 2903.62 11" Youth Field Master Glove Saturday 3636.85 11" Youth Field Master Glove Sunday 6602.18 11" Youth Field Master Glove Thursday 5696.37 11" Youth Field Master Glove Tuesday 2843.81 11" Youth Field Master Glove Wednesday 6072.04 11.5" Youth Triple Stripe Series Glove Friday 6695.84 11.5" Youth Triple Stripe Series Glove Monday 5436.28 11.5" Youth Triple Stripe Series Glove Saturday 5653.8 11.5" Youth Triple Stripe Series Glove Sunday 10909.86 ... ... multiple rows returned ... ... PROD_NAME DAY_NAME SUM(S.AMOUNT_SOLD) -------------------------------------------------- --------- ------------------ Wicket Keeper Gloves Thursday 1550.94 Wicket Keeper Gloves Tuesday 3049.62 Wicket Keeper Gloves Wednesday 2583.16 Wide Brim Hat Friday 189.28 Wide Brim Hat Monday 1656.35 Wide Brim Hat Saturday 1689.48 Wide Brim Hat Sunday 560.7 Wide Brim Hat Thursday 1088.44 Wide Brim Hat Tuesday 2855.67 Wide Brim Hat Wednesday 250.19 461 rows selected. SQL>
This helps developers who already use the Column Position in the ORDER BY clause and can be consistent when writing the GROUP BY clause.
The HAVING clause also supports Column Aliases.
Categories: DBA Blogs
Using Oracle's Autonomous Health Framework to get an "Insight" into a RAC Cluster
I've posted a video demonstration on using Oracle's Autonomous Health Framework ("AHF") get an "Insight" into a RAC Cluster.
AHF (Oracle Support Doc ID 2550798.1) is Oracle's current diagnostic tool which includes Orachk and TFA (Trace File Analyzer). Explore it.
Categories: DBA Blogs
Video on DataGuard Snapshot Standby
I have posted a new video on creating a "Snapshot Standby" database in DataGuard.
Typically such a Standby can be used for "destructive testing" like D.R. simulation with dummy transactions, application upgrades, schema changes.
If your concern is about the Physical Standby being unavailable for long note :
(1) Redo Shipping to the Standby can continue as ArchiveLogs (of course, this means the Standby will be lagging the Primary by the typical interval between Archive Log switches)
(2) You can configure 2 Standbys of which one continues to be a Physical Standby with real time redo shipping and the other is periodically used to test schema changes / application upgrades and even for frequent D.R. testing
I have previously posted a few Blog posts on scenarios like Multiple Standbys, Standbys with Lag, Destructive testing in Standbys. See the list of posts here.
Categories: DBA Blogs
Video on DataGuard Switchover -- with RAC and Single Instance
I've posted a demonstration of DataGuard Switchover, using RAC and Single Instance as the Primary/Standby pair.
Fundamentally, there is no difference if either or both of the databases are RAC or Single Instance.
A Switchover is a Graceful operation, with No-Data-Loss as the Primary sends the "End-Of-Redo Marker" to the Standby at which point Reversal of Roles happens. Therefore, you can execute Switchover between the two databases (servers / data centres / sites) multiple times without loss of data.
A Failover, on the other hand, involves data loss and the erstwhile Primary does not revert to a Standby role but must be recreated / refreshed as a Standby from the new Primary.
Categories: DBA Blogs
A few dgmgrl (DataGuard Broker) commands
I haven't create a video with commentary but here are a few dgmgrl commands.
In the output "RACDB" (or "racdb") is a 2-node RAC database (managed by ClusterWare) and "STDBY" (or "stdby") is a Single Node non-RAC database not using Oracle Restart. Both are 19c (19.23)
Initial Setup :
[oracle@srv1 ~]$ dgmgrl sys
DGMGRL for Linux: Release 19.0.0.0.0 - Production on Sat Jul 27 02:31:53 2024
Version 19.23.0.0.0
Copyright (c) 1982, 2019, Oracle and/or its affiliates. All rights reserved.
Welcome to DGMGRL, type "help" for information.
Password:
Connected to "RACDB"
Connected as SYSDBA.
DGMGRL> remove configuration;
Removed configuration
DGMGRL> create configuration racdb_dg as primary database is RACDB connect identifier is RACDB;
Configuration "racdb_dg" created with primary database "racdb"
DGMGRL> add database STDBY as connect identifier is STDBY maintained as physical;
Database "stdby" added
DGMGRL> show configuration;
Configuration - racdb_dg
Protection Mode: MaxPerformance
Members:
racdb - Primary database
stdby - Physical standby database
Fast-Start Failover: Disabled
Configuration Status:
DISABLED
DGMGRL> enable configuration;
Enabled.
DGMGRL> show configuration;
Configuration - racdb_dg
Protection Mode: MaxPerformance
Members:
racdb - Primary database
Warning: ORA-16905: The member was not enabled yet.
stdby - Physical standby database
Fast-Start Failover: Disabled
Configuration Status:
WARNING (status updated 177 seconds ago)
DGMGRL> show configuration ;
Configuration - racdb_dg
Protection Mode: MaxPerformance
Members:
racdb - Primary database
Warning: ORA-16905: The member was not enabled yet.
stdby - Physical standby database
Fast-Start Failover: Disabled
Configuration Status:
WARNING (status updated 182 seconds ago)
DGMGRL>
DGMGRL> show configuration ;
Configuration - racdb_dg
Protection Mode: MaxPerformance
Members:
racdb - Primary database
stdby - Physical standby database
Fast-Start Failover: Disabled
Configuration Status:
SUCCESS (status updated 44 seconds ago)
DGMGRL>
DGMGRL> show configuration lag;
Configuration - racdb_dg
Protection Mode: MaxPerformance
Members:
racdb - Primary database
stdby - Physical standby database
Transport Lag: 0 seconds (computed 0 seconds ago)
Apply Lag: 0 seconds (computed 0 seconds ago)
Fast-Start Failover: Disabled
Configuration Status:
SUCCESS (status updated 23 seconds ago)
DGMGRL>
In the initial setup, it takes time to actually enable the databases so we see the "ORA-16095: the member was not enabled yet" warning messages.Later, it takes time for communication of the Transport and Apply lag information so I present the lag only some significant seconds later.
Note that DataGuard is configured as "Maximum Performance" mode (not Maximum Availability as I show in my previous video)
The VALIDATE commands :
GMGRL> validate database racdb;
Database Role: Primary database
Ready for Switchover: Yes
Managed by Clusterware:
racdb: YES
DGMGRL> validate database stdby;
Database Role: Physical standby database
Primary Database: racdb
Ready for Switchover: Yes
Ready for Failover: Yes (Primary Running)
Flashback Database Status:
racdb: On
stdby: Off
Capacity Information:
Database Instances Threads
racdb 2 2
stdby 1 2
Warning: the target standby has fewer instances than the
primary database, this may impact application performance
Managed by Clusterware:
racdb: YES
stdby: NO
Current Configuration Log File Sizes:
Thread # Smallest Online Redo Smallest Standby Redo
Log File Size Log File Size
(racdb) (stdby)
1 512 MBytes 100 MBytes
2 512 MBytes 100 MBytes
DGMGRL>
Here we see some information :(1) The configuration is Ready for Swtichover (from "racdb" as Primary to "stdb")
(2) Flashback Database is configured on "racdb" but not on "stdby"
(3) Although "racdb" has two instances (two redo threads), "stdby" has only 1 instance (and redo thread) {Thus we know it is possible to have a Single Instance Standby Database for a MultiNode RAC --- I won't go into a debate / discussion on such a configuration if comments appear in response to this blog post, suffice to say that IMHO, it can make sense to do so}
(4) "racdb" is managed by ClusterWare but "stdby" is not {Thus we know that the Standby does not have to be in ClusterWare / Oracle Restart configuration}
(5) Although "racdb" has Redo Log files of 512MB, "stdby" is, unfortunately, configured with some smaller Redo Logs
Some "Verbose" Configuration Information :
DGMGRL> show configuration verbose
Configuration - racdb_dg
Protection Mode: MaxPerformance
Members:
racdb - Primary database
stdby - Physical standby database
Properties:
FastStartFailoverThreshold = '30'
OperationTimeout = '30'
TraceLevel = 'USER'
FastStartFailoverLagLimit = '30'
CommunicationTimeout = '180'
ObserverReconnect = '0'
FastStartFailoverLagGraceTime = '0'
FastStartFailoverAutoReinstate = 'TRUE'
FastStartFailoverPmyShutdown = 'TRUE'
BystandersFollowRoleChange = 'ALL'
ObserverOverride = 'FALSE'
ExternalDestination1 = ''
ExternalDestination2 = ''
PrimaryLostWriteAction = 'CONTINUE'
ConfigurationWideServiceName = 'RACDB_CFG'
FastStartFailoverLagType = 'APPLY'
Fast-Start Failover: Disabled
Configuration Status:
SUCCESS
DGMGRL>
DGMGRL> show database verbose racdb;
Database - racdb
Role: PRIMARY
Intended State: TRANSPORT-ON
Instance(s):
RACDB1
RACDB2
Properties:
DGConnectIdentifier = 'racdb'
ObserverConnectIdentifier = ''
FastStartFailoverTarget = ''
PreferredObserverHosts = ''
LogShipping = 'ON'
RedoRoutes = ''
LogXptMode = 'ASYNC'
DelayMins = '0'
Binding = 'optional'
MaxFailure = '0'
ReopenSecs = '300'
NetTimeout = '30'
RedoCompression = 'DISABLE'
PreferredApplyInstance = ''
ApplyInstanceTimeout = '0'
ApplyLagThreshold = '30'
TransportLagThreshold = '30'
TransportDisconnectedThreshold = '30'
ApplyParallel = 'AUTO'
ApplyInstances = '0'
StandbyFileManagement = ''
ArchiveLagTarget = '0'
LogArchiveMaxProcesses = '0'
LogArchiveMinSucceedDest = '0'
DataGuardSyncLatency = '0'
LogArchiveTrace = '0'
LogArchiveFormat = ''
DbFileNameConvert = ''
LogFileNameConvert = ''
ArchiveLocation = ''
AlternateLocation = ''
StandbyArchiveLocation = ''
StandbyAlternateLocation = ''
InconsistentProperties = '(monitor)'
InconsistentLogXptProps = '(monitor)'
LogXptStatus = '(monitor)'
SendQEntries = '(monitor)'
RecvQEntries = '(monitor)'
HostName(*)
StaticConnectIdentifier(*)
TopWaitEvents(*)
SidName(*)
(*) - Please check specific instance for the property value
Log file locations(*):
(*) - Check specific instance for log file locations.
Database Status:
SUCCESS
DGMGRL>
DGMGRL> show instance verbose "RACDB1"
Instance 'RACDB1' of database 'racdb'
PFILE:
Properties:
HostName = 'srv1'
StaticConnectIdentifier = '(DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=192.168.56.91)(PORT=1521))(CONNECT_DATA=(SERVICE_NAME=RACDB_DGMGRL)(INSTANCE_NAME=RACDB1)(SERVER=DEDICATED)))'
TopWaitEvents = '(monitor)'
SidName = '(monitor)'
Log file locations:
Alert log : /u01/app/oracle/diag/rdbms/racdb/RACDB1/trace/alert_RACDB1.log
Data Guard Broker log : /u01/app/oracle/diag/rdbms/racdb/RACDB1/trace/drcRACDB1.log
Instance Status:
SUCCESS
DGMGRL>
Here we see some more information :(1) Timeouts (which I've left at defaults)
(2) Fast Start Failover and Observer information (which I am not using in this configuration)
(3) That Log Transport is Async, with 0 Delay and Compression Disabled.
(3) The Alert Log and DG Broker Log file location (for "racdb", I extract the information for only the first instance, "RACDB1")
Connect Identifiers :
DGMGRL> validate static connect identifier for racdb; Oracle Clusterware on database "racdb" is available for database restart. DGMGRL> validate static connect identifier for stdby; Oracle Clusterware is not configured on database "stdby". Connecting to database "stdby" using static connect identifier "(DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=stdby)(PORT=1521))(CONNECT_DATA=(SERVICE_NAME=STDBY_DGMGRL)(INSTANCE_NAME=STDBY)(SERVER=DEDICATED)(STATIC_SERVICE=TRUE)))" ... Succeeded. The static connect identifier allows for a connection to database "stdby".For "racdb" being managed by ClusterWare, I had specified "RACDB" {which is the SCAN address} as the Connect Identifier (with "primary database is RACDB connect identifier is RACDB" in the first configuration command) For "stdby", not being managed by ClusterWare or Oracle Restart, it DGMGRL entry for the Listener is required in this manner :
SID_LIST_LISTENER =
(SID_LIST =
(SID_DESC =
(GLOBAL_DBNAME = STDBY)
(SID_NAME = STDBY)
(ORACLE_HOME = /u01/app/oracle/product/19.0.0/dbhome_1)
)
(SID_DESC =
(GLOBAL_DBNAME = STDBY_DGMGRL)
(SID_NAME = STDBY)
(ORACLE_HOME = /u01/app/oracle/product/19.0.0/dbhome_1)
(ENVS="TNS_ADMIN=/u01/app/oracle/product/19.0.0/dbhome_1/network/admin")
)
)
So, if either your Primary or Standby or both are Not managed by ClusterWare or Oracle Restart, you need to have a DGMGRL entry for the Listener !
Categories: DBA Blogs
Video on OCR and OLR commands in RAC GI/ClusterWare
Last week I published a new video on OCR and OLR commands.
ocrcheck : Lists the locations of the OCR and checks for corruption (run as root to check for logical corruption as well)
ocrconfig -add DG Name (e.g. ocrconfig -add +DATA) : Adds a new copy of the OCR in the stated ASM DG
ocrconfig -delete DG Name : Deletes a copy of the OCR from the ASM DG
cat /etc/oracle/olr.loc : Shows the location of the OLR
ocrcheck -local : Checks the OLR
ocrconfig -showbackup : Shows the default location of OCR backups
ocrconfig -manualbackup : Create a manual backup of the OCR
(use asmcmd to copy the backup out from ASM to Filesystem)
ocrconfig -local -showbackuploc : Shows the location of OLR backups
ocrconfig -local -manualbackup : Create a manual backup of the OLR
ocrconfig -local -export : Create an Export backup of the OLR
Categories: DBA Blogs
Video on the Maximum Availability Protection Mode in Oracle DataGuard (with RAC)
I've published a new video demonstrating Maximum Availability Protection Mode in Oracle DataGuard.
Categories: DBA Blogs
Testing updated ORA-942 Error Message in 23ai
Oracle 23ai now has a long-requested fix to the ORA-942 "table or view does not exist" error message. The error message would not print out *which* table or view was missing -- this was particularly troublesome with very long SQL statements and multiple tables and views being referenced.
A demo of the fixed behaviour in 23ai (followed later by the same code in 19c 19.22)
SQL> select banner from v$version;
BANNER
---------------------------------------------------------------------------------------------------------------------------------
Oracle Database 23ai Free Release 23.0.0.0.0 - Develop, Learn, and Run for Free
SQL>
SQL> -- create the two tables
SQL> drop table employees;
drop table employees
*
ERROR at line 1:
ORA-00942: table or view "HEMANT"."EMPLOYEES" does not exist
Help: https://docs.oracle.com/error-help/db/ora-00942/
SQL> drop table departments;
Table dropped.
SQL> create table departments (dept_id number(12) primary key, dept_name varchar2(30));
Table created.
SQL> create table employees (emp_id number(12) primary key, emp_name varchar2(54), dept_id number(12));
Table created.
SQL>
SQL> -- insert data
SQL> insert into departments values (1,'Human Resources');
1 row created.
SQL> insert into employees values (1,'Somebody',1);
1 row created.
SQL> commit;
Commit complete.
SQL>
SQL> -- test query
SQL> select d.dept_id, d.dept_name, e.emp_name
2 from departments d, employees e
3 where e.dept_id = d.dept_id
4 order by d.dept_id,e.emp_name
5 /
DEPT_ID DEPT_NAME EMP_NAME
---------- ------------------------------ ------------------------------------------------------
1 Human Resources Somebody
SQL>
SQL> -- drop a table
SQL> drop table employees;
Table dropped.
SQL>
SQL> -- RETEST query
SQL> select d.dept_id, d.dept_name, e.emp_name
2 from departments d, employees e
3 where e.dept_id = d.dept_id
4 order by d.dept_id,e.emp_name
5 /
from departments d, employees e
*
ERROR at line 2:
ORA-00942: table or view "HEMANT"."EMPLOYEES" does not exist
Help: https://docs.oracle.com/error-help/db/ora-00942/
SQL>
So, now the error message text for ORA-942 includes the name of the missing <schema>.<table_or_view>
Here is the same code in 19c (19.22)
SQL> --select banner from v$version;
SQL> -- use BANNER_FULL in 19c to get RU level -- 19.22
SQL> select banner_full from v$version;
BANNER_FULL
------------------------------------------------------------------------------------------------------------------------------------
Oracle Database 19c Enterprise Edition Release 19.0.0.0.0 - Production
Version 19.22.0.0.0
SQL>
SQL> -- create the two tables
SQL> drop table employees;
drop table employees
*
ERROR at line 1:
ORA-00942: table or view does not exist
SQL> drop table departments;
Table dropped.
SQL> create table departments (dept_id number(12) primary key, dept_name varchar2(30));
Table created.
SQL> create table employees (emp_id number(12) primary key, emp_name varchar2(54), dept_id number(12));
Table created.
SQL>
SQL> -- insert data
SQL> insert into departments values (1,'Human Resources');
1 row created.
SQL> insert into employees values (1,'Somebody',1);
1 row created.
SQL> commit;
Commit complete.
SQL>
SQL> -- test query
SQL> select d.dept_id, d.dept_name, e.emp_name
2 from departments d, employees e
3 where e.dept_id = d.dept_id
4 order by d.dept_id,e.emp_name
5 /
DEPT_ID DEPT_NAME EMP_NAME
---------- ------------------------------ ------------------------------------------------------
1 Human Resources Somebody
SQL>
SQL> -- drop a table
SQL> drop table employees;
Table dropped.
SQL>
SQL> -- RETEST query
SQL> select d.dept_id, d.dept_name, e.emp_name
2 from departments d, employees e
3 where e.dept_id = d.dept_id
4 order by d.dept_id,e.emp_name
5 /
from departments d, employees e
*
ERROR at line 2:
ORA-00942: table or view does not exist
SQL>
So, upto 19c, ORA-942 would simply say "table or view does not exist". In my example using sqlplus and a very short from list, the "*" does indicate where the error is -- but with other tools / clients and long FROM or sub-queries with FROM clauses, it may well be difficult to identify the missing table or view unless you trace the execution or run a test query against each table or view.
Categories: DBA Blogs
Testing Open a PDB as a Hybrid Read Only PDB in 23ai
Oracle 23ai now allows the DBA to open a PDB in Hybrid Read Only mode. This mode allows Common Users (e.g. SYS or SYSTEM or others defined as Common Users from the Root CDB) to access a PDB in Read-Write mode while local (i.e. non-Common Users) can access the PDB only in Read-Only mode.
This facilitates live maintenance (e.g. patching or changes to the database / schema) being executed by a DBA or Common User while "normal" local users (eg. Application Accounts) can still query the database.
This is a quick demo :
SQL> -- open the PDB as "normal" Read Write
SQL> connect / as sysdba
Connected.
SQL> -- Version 23ai Free Edition
SQL> select banner from v$version;
BANNER
--------------------------------------------------------------------------------
Oracle Database 23ai Free Release 23.0.0.0.0 - Develop, Learn, and Run for Free
SQL>
SQL> alter pluggable database freepdb1 close;
Pluggable database altered.
SQL> alter pluggable database freepdb1 open;
Pluggable database altered.
SQL>
SQL> -- first demo a normal user in the PDB
SQL> connect hemant/hemant@freepdb1
Connected.
SQL> create table x_test (id number , data varchar2(15));
Table created.
SQL> insert into x_test values (1,'First');
1 row created.
SQL> commit;
Commit complete.
SQL> select * from hemant.x_test order by 1;
ID DATA
---------- ---------------
1 First
SQL>
SQL>
SQL> -- now close and open the PDB in Hybrid Read Only mode
SQL> connect / as sysdba
Connected.
SQL> alter pluggable database freepdb1 close;
Pluggable database altered.
SQL> alter pluggable database freepdb1 open hybrid read only ;
Pluggable database altered.
SQL> -- test that SYSTEM (a Common User) can manipulate data -- e.g. INSERT
SQL> connect system/manager@freepdb1
Connected.
SQL> insert into hemant.x_test values(2,'System');
1 row created.
SQL> commit;
Commit complete.
SQL> select * from hemant.x_test order by 1;
ID DATA
---------- ---------------
1 First
2 System
SQL> -- even grant DBA to hemant
SQL> grant dba to hemant;
Grant succeeded.
SQL>
SQL> -- test hemant a non-common user
SQL> -- see if the user can execute INSERT and SELECT
SQL> connect hemant/hemant@freepdb1
Connected.
SQL> insert into hemant.x_test values(3,'Third');
insert into hemant.x_test values(3,'Third')
*
ERROR at line 1:
ORA-16000: Attempting to modify database or pluggable database that is open for
read-only access.
Help: https://docs.oracle.com/error-help/db/ora-16000/
SQL> commit;
Commit complete.
SQL> select * from hemant.x_test order by 1;
ID DATA
---------- ---------------
1 First
2 System
SQL> -- so SELECT works, but not INSERT
SQL>
SQL>
SQL> -- reopen PDB as normal "Read Write"
SQL> connect / as sysdba
Connected.
SQL> alter pluggable database freepdb1 close;
Pluggable database altered.
SQL> alter pluggable database freepdb1 open;
Pluggable database altered.
SQL> connect hemant/hemant@freepdb1
Connected.
SQL> insert into hemant.x_test values(4,'Fourth');
1 row created.
SQL> commit;
Commit complete.
SQL> select * from hemant.x_test order by 1;
ID DATA
---------- ---------------
1 First
2 System
4 Fourth
SQL>
Thus, when the PDB was first opened in "normal" mode (ie the default OPEN mode is OPEN READ WRITE), the local user "HEMANT" could execute DDL and DML (create the table and Insert).
When it was reopened in Hybrid Read Only Mode, the user could not make changes (insert the row with ID=3) but could still query the data (even if the user has been granted "DBA"). However, the Common User "SYSTEM" was allowed to insert the row with ID=2, DATA='SYSTEM'.
Finally, reopening the PDB in "normal" OPEN READ WRITE mode, the user "HEMANT" could again insert a row (ID=4)
Categories: DBA Blogs
Testing RENAME LOB (Segment) in 23ai
Another new feature of 23ai is the ability to rename a LOB (Segment) in-place without having to use the MOVE clause.
A quick demo :
SQL> -- Version 23ai Free Edition
SQL> select banner from v$version;
BANNER
---------------------------------------------------------------------------------------------------------------------------------
Oracle Database 23ai Free Release 23.0.0.0.0 - Develop, Learn, and Run for Free
SQL>
SQL>
SQL> DROP TABLE my_lob_objects purge;
Table dropped.
SQL>
SQL> -- create the table with a LOB, column name "c", lob segment name also "c"
SQL> CREATE TABLE my_lob_objects (object_id NUMBER primary key, c CLOB)
2 lob (c) STORE AS SECUREFILE c
3 ( TABLESPACE users
4 DISABLE STORAGE IN ROW
5 NOCACHE LOGGING
6 RETENTION AUTO
7 COMPRESS
8 );
Table created.
SQL>
SQL> -- query the data dictionary
SQL> select table_name, column_name, segment_name, tablespace_name from user_lobs;
TABLE_NAME COLUMN_NAME SEGMENT_NAME TABLESPACE_NAME
---------------- ---------------- -------------------- ----------------
MY_LOB_OBJECTS C C USERS
SQL>
SQL> -- insert three rows
SQL> insert into my_lob_objects values (1, dbms_random.string('X',100));
1 row created.
SQL> insert into my_lob_objects values (2, dbms_random.string('X',100));
1 row created.
SQL> insert into my_lob_objects values (3, dbms_random.string('X',100));
1 row created.
SQL>
SQL> -- verify the column name when querying the table
SQL> select * from my_lob_objects;
OBJECT_ID C
---------- --------------------------------------------------------------------------------
1 IBGOGKA9QKK56O746IJL3C56ZK9LEO0G1W4LWBN11T8EWCFTTLUW9TPIVQAU8BPSGPQ2ZV57BS0ZPK0S
2 7K04DVVYDQB1URIQ1OQ2458M8ZOURHWW50XIZDMVGAZH6XVN2KKN4PIGKPY5CSVIQ9KU45LHZPJB33AA
3 2G5194Z7TSR3XG0K698G587AOZOJ8VN6KFCTCH3074TNCOWCSMOPRJLRGTLIZMDD73XAY4KDD14IW4MG
SQL>
SQL> -- now rename the column
SQL> alter table my_lob_objects rename column c to clob_col;
Table altered.
SQL>
SQL> -- query the data dictionary
SQL> select table_name, column_name, segment_name, tablespace_name from user_lobs;
TABLE_NAME COLUMN_NAME SEGMENT_NAME TABLESPACE_NAME
---------------- ---------------- -------------------- ----------------
MY_LOB_OBJECTS CLOB_COL C USERS
SQL>
SQL> -- now rename the lob segment
SQL> alter table my_lob_objects rename lob(clob_col) c to my_lob_objects_clob;
Table altered.
SQL>
SQL> -- query the data dictionary
SQL> select table_name, column_name, segment_name, tablespace_name from user_lobs;
TABLE_NAME COLUMN_NAME SEGMENT_NAME TABLESPACE_NAME
---------------- ---------------- -------------------- ----------------
MY_LOB_OBJECTS CLOB_COL MY_LOB_OBJECTS_CLOB USERS
SQL>
SQL> -- verify the column name when querying the table
SQL> select * from my_lob_objects;
OBJECT_ID CLOB_COL
---------- --------------------------------------------------------------------------------
1 IBGOGKA9QKK56O746IJL3C56ZK9LEO0G1W4LWBN11T8EWCFTTLUW9TPIVQAU8BPSGPQ2ZV57BS0ZPK0S
2 7K04DVVYDQB1URIQ1OQ2458M8ZOURHWW50XIZDMVGAZH6XVN2KKN4PIGKPY5CSVIQ9KU45LHZPJB33AA
3 2G5194Z7TSR3XG0K698G587AOZOJ8VN6KFCTCH3074TNCOWCSMOPRJLRGTLIZMDD73XAY4KDD14IW4MG
SQL>
SQL> -- identify the segment
SQL> select tablespace_name, segment_name, segment_type, bytes/1024 Size_KB
2 from user_segments
3 where segment_name = 'MY_LOB_OBJECTS_CLOB'
4 /
TABLESPACE_NAME SEGMENT_NAME SEGMENT_TYPE SIZE_KB
---------------- -------------------- ------------------ ---------
USERS MY_LOB_OBJECTS_CLOB LOBSEGMENT 2304
SQL>
First I create a Table where the Column and LOB (Segment) are both called "C". In recent versions, SECUREFILE is the default and recommended for LOBs (e.g. with the COMPRESS, DEDUPLICATION and ENCRYPTION advantages).
Then I insert 3 rows.
I then rename the column "C" to "CLOB_COL".
Next, I rename the LOB (Segment) to "MY_LOB_OBJECTS_CLOB". I include the Table Name because the LOB segment is an independent segment that I might query in USER_SEGMENTS (where Table Name) is not available. This RENAME LOB clause is new in 23ai and does not require the use of MOVE LOB.
I then verify the new Segment Name for the LOB as well.
Yes, the 2,304KB "size" seems excessive but this will make sense (with the COMPRESS attribute) when the LOB grows much much larger as new rows with long Character-Strings are inserted.
Categories: DBA Blogs
Testing DEFAULT ON NULL FOR UPDATE in 23ai
Testing a new feature in 23ai that allows you to define a DEFAULT value for a column if a user/front-end/application sends a NULL :
[oracle@oel9 ~]$ sqlplus hemant/hemant@freepdb1
SQL*Plus: Release 23.0.0.0.0 - Production on Thu May 9 14:54:25 2024
Version 23.4.0.24.05
Copyright (c) 1982, 2024, Oracle. All rights reserved.
Connected to:
Oracle Database 23ai Free Release 23.0.0.0.0 - Develop, Learn, and Run for Free
Version 23.4.0.24.05
SQL> create table my_new_employees(
2 employee_id number(12) primary key,
3 employee_name varchar2(48),
4 department_id number(12)
5 )
6 /
Table created.
SQL>
SQL> insert into my_new_employees
2 values (1,'Hemant',NULL)
3 /
1 row created.
SQL>
SQL> select * from my_new_employees;
EMPLOYEE_ID EMPLOYEE_NAME DEPARTMENT_ID
----------- ------------------------------------------------ -------------
1 Hemant
SQL>
SQL> update my_new_employees
2 set department_id=100 -- setting a non-NULL value
3 where employee_id=1
4 /
1 row updated.
SQL> select * from my_new_employees;
EMPLOYEE_ID EMPLOYEE_NAME DEPARTMENT_ID
----------- ------------------------------------------------ -------------
1 Hemant 100
SQL>
SQL> alter table my_new_employees
2 modify (department_id default on null for insert and update 512);
Table altered.
SQL> insert into my_new_employees
2 values (2,'Larry'); -- I am not specifying a value for DEPARTMENT_ID
insert into my_new_employees
*
ERROR at line 1:
ORA-00947: not enough values
Help: https://docs.oracle.com/error-help/db/ora-00947/
SQL> insert into my_new_employees
2 values(2,'Larry', NULL); -- I explicitly specify NULL for DEPARTMENT_ID
1 row created.
SQL> select * from my_new_employees order by 1;
EMPLOYEE_ID EMPLOYEE_NAME DEPARTMENT_ID
----------- ------------------------------------------------ -------------
1 Hemant 100
2 Larry 512 -- it got set to 512 ON INSERT
SQL>
SQL> update my_new_employees
2 set employee_name = 'Hemant Chitale', department_id=NULL -- I explicitly specify NULL for DEPARMTENT_ID
3 where employee_id=1
4 /
1 row updated.
SQL> select * from my_new_employees order by 1;
EMPLOYEE_ID EMPLOYEE_NAME DEPARTMENT_ID
----------- ------------------------------------------------ -------------
1 Hemant Chitale 512 -- it got set to 512 ON UPDATE
2 Larry 512
SQL>
SQL> commit;
Commit complete.
SQL> select * from my_new_employees order by 1;
EMPLOYEE_ID EMPLOYEE_NAME DEPARTMENT_ID
----------- ------------------------------------------------ -------------
1 Hemant Chitale 512
2 Larry 512
SQL>
So, now the column has a proper DEFAULT value when an UPDATE statement sends a NULL. This allows the developer to avoid having to write a Front-End Value Check or a Database Table Trigger to convert an incoming NULL to a DEFAULT value.
Categories: DBA Blogs
Testing DB_FLASHBACK_LOG_DEST in 23ai
Pre-23ai, Database Flashback Logs always were created in the DB_RECOVERY_FILE_DEST location (i.e.. the well-known "Fast Recovery Area" also known as "FRA").
However, these would share space with ArchiveLogs (if you've configured ArchiveLogs to the same location) and RMAN Backups (if you aren't specifically writing RMAN Backups to a different location).
23ai introduced the DB_FLASHBACK_LOG_DEST (and corresponding DB_FLASHBACK_LOG_DEST_SIZE) parameter to allow you to separate your Database Flashback Logs to a dedicated location.
The 23ai New Features documentation has this to say :
In previous releases, you could store flashback database logs only in the fast recovery area. Now you can optionally designate a separate location for flashback logging. For example, if you have write-intensive database workloads, then flashback database logging can slow down the database if the fast recovery area is not fast enough. In this scenario, you can now choose to write the flashback logs to faster disks. Using a separate destination also eliminates the manual administration to manage the free space in the fast recovery area.
Managing flashback database logs outside the fast recovery area lowers the operational costs related to space management and guarantees the best performance for workloads that are typically impacted by flashback logging on traditional storage.
And it provides a link to the documentation on the parameter.
You might think that DB_FLASHBACK_LOG_DEST is now completely independent of DB_RECOVERY_FILE_DEST.
Here is my test run where I configured DB_FLASHBACK_LOG_DEST without configuring DB_RECOVERY_FILE_DEST :
h-4.4$ cd /opt/oracle
sh-4.4$ mkdir FBL
sh-4.4$ mkdir FRA
sh-4.4$ sqlplus / as sysdba
SQL*Plus: Release 23.0.0.0.0 - Production on Sun May 5 10:26:26 2024
Version 23.4.0.24.05
Copyright (c) 1982, 2024, Oracle. All rights reserved.
Connected to:
Oracle Database 23ai Free Release 23.0.0.0.0 - Develop, Learn, and Run for Free
Version 23.4.0.24.05
SQL> shutdown immediate;
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL> startup mount
ORACLE instance started.
Total System Global Area 1603726344 bytes
Fixed Size 5360648 bytes
Variable Size 402653184 bytes
Database Buffers 1191182336 bytes
Redo Buffers 4530176 bytes
Database mounted.
SQL> show parameter spfile;
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
spfile string /opt/oracle/product/23ai/dbhom
eFree/dbs/spfileFREE.ora
SQL>
SQL> alter database archivelog;
Database altered.
SQL> alter database open;
Database altered.
SQL> show parameter db_flashback
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
db_flashback_log_dest string
db_flashback_log_dest_size big integer 0
SQL> alter system set db_flashback_log_dest_size=10G;
System altered.
SQL> alter system set db_flashback_log_dest='/opt/oracle/FBL';
System altered.
SQL> create restore point MY_FIRST_RP ;
Restore point created.
SQL> alter system archive log current;
System altered.
SQL>
SQL> create table x as select * from cdb_objects;
Table created.
SQL> insert into x select * from x;
141420 rows created.
SQL> delete x;
282840 rows deleted.
SQL> commit;
Commit complete.
SQL> alter system archive log current;
System altered.
SQL>
SQL> alter database flashback on; -- only here I enable Flashback
Database altered.
==============================================
alert log messages :
2024-05-05T10:38:35.262274+00:00
alter database flashback on
2024-05-05T10:38:35.423698+00:00
Allocating 8388608 bytes in shared pool for flashback generation buffer.
Allocated 8388608 bytes in shared pool for flashback generation buffer
Flashback Database Enabled at SCN 3124894
===============================================
SQL> create restore point MY_FIRST_RP; -- testing if I can create another RP with the same name
create restore point MY_FIRST_RP
*
ERROR at line 1:
ORA-38778: Restore point 'MY_FIRST_RP' already exists.
Help: https://docs.oracle.com/error-help/db/ora-38778/
SQL> drop restore point MY_FIRST_RP;
Restore point dropped.
SQL> create restore point MY_FIRST_RP;
Restore point created.
SQL> drop table x;
Table dropped.
SQL> create table x as select * from cdb_objects;
Table created.
SQL>
SQL> alter system archive log current;
System altered.
SQL> delete x;
141420 rows deleted.
SQL> insert into x select * from cdb_objects;
141421 rows created.
SQL> commit;
Commit complete.
SQL> alter system archive log current;
System altered.
SQL>
SQL> select substr(name,1,32), scn, time from v$restore_point; -- identify the RP that has been created
SUBSTR(NAME,1,32)
--------------------------------------------------------------------------------------------------------------------------------
SCN TIME
---------- ---------------------------------------------------------------------------
MY_FIRST_RP
3124955 05-MAY-24 10.39.30.000000000 AM
SQL> select * from v$flashback_database_log; -- identify the FBDB Logs Size
OLDEST_FLASHBACK_SCN OLDEST_FL RETENTION_TARGET FLASHBACK_SIZE ESTIMATED_FLASHBACK_SIZE CON_ID
-------------------- --------- ---------------- -------------- ------------------------ ----------
3124893 05-MAY-24 1440 419430400 0 0
SQL> select * from v$flashback_log_dest; -- identify the FB Log Dest (why isn't the view named V$FLASHBACK_DATABASE_LOG_DEST ?)
NAME
------------------------------------------------------------------------------------------------------------------------------------
SPACE_LIMIT SPACE_USED NUMBER_OF_FILES CON_ID
----------- ---------- --------------- ----------
/opt/oracle/FBL
1.0737E+10 419430400 2 0
SQL>
SQL> !sh
sh-4.4$ cd /opt/oracle/FBL
sh-4.4$ du -sh *
401M FREE
sh-4.4$ cd FREE
sh-4.4$ ls
flashback
sh-4.4$ cd flashback
sh-4.4$ ls -l
total 409620
-rw-r----- 1 oracle oinstall 209723392 May 5 10:41 o1_mf_m3grfc8t_.flb
-rw-r----- 1 oracle oinstall 209723392 May 5 10:38 o1_mf_m3grfg1v_.flb
sh-4.4$
sh-4.4$ cd $ORACLE_HOME/dbs
sh-4.4$ ls -l arch1*
-rw-r----- 1 oracle oinstall 98164736 May 5 10:31 arch1_2_1167168121.dbf
-rw-r----- 1 oracle oinstall 106480640 May 5 10:33 arch1_3_1167168121.dbf
-rw-r----- 1 oracle oinstall 37506048 May 5 10:40 arch1_4_1167168121.dbf
-rw-r----- 1 oracle oinstall 52515840 May 5 10:40 arch1_5_1167168121.dbf
sh-4.4$
sh-4.4$ exit
exit
SQL> select count(*) from x;
COUNT(*)
----------
141421
SQL> shutdown immediate;
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL>
SQL> startup mount;
ORACLE instance started.
Total System Global Area 1603726344 bytes
Fixed Size 5360648 bytes
Variable Size 419430400 bytes
Database Buffers 1174405120 bytes
Redo Buffers 4530176 bytes
Database mounted.
SQL> flashback database to restore point MY_FIRST_RP; -- try to Flashback the Database
flashback database to restore point MY_FIRST_RP
*
ERROR at line 1:
ORA-38760: This database instance failed to turn on flashback database
Help: https://docs.oracle.com/error-help/db/ora-38760/
============================================
alert log messages :
2024-05-05T10:45:28.380285+00:00
Successful mount of redo thread 1, with mount id 1440201864
2024-05-05T10:45:28.380506+00:00
Allocating 8388608 bytes in shared pool for flashback generation buffer.
Allocated 5807328 bytes in shared pool for flashback generation buffer
RVWR could not begin generation of flashback log data because
DB_RECOVERY_FILE_DEST is not set.
2024-05-05T10:45:28.392865+00:00
Errors in file /opt/oracle/diag/rdbms/free/FREE/trace/FREE_rvwr_2343.trc:
ORA-38776: cannot begin flashback generation - recovery area is disabled
2024-05-05T10:45:28.392899+00:00
WARNING: Cannot open the flashback thread for this instance due to the above error.
WARNING: Flashback thread open failed - to resolve this, either correct the reported error or turn off database flashbac
k.
2024-05-05T10:45:28.393060+00:00
Database mounted in Exclusive Mode
Lost write protection mode set to "auto"
Completed: ALTER DATABASE MOUNT
2024-05-05T10:46:04.458087+00:00
flashback database to restore point MY_FIRST_RP
ORA-38760 signalled during: flashback database to restore point MY_FIRST_RP...
2024-05-05T10:50:43.887137+00:00
==============================================
Explanation of the Error :
===========================
38776, 00000, "cannot begin flashback generation - recovery area is disabled"
// *Cause: During a database mount, the RVWR process discovered that the
// recovery area was disabled. DB_RECOVERY_FILE_DEST must have
// been set null or removed from the INIT.ORA file while the database
// was unmounted.
// *Action: Flashback database requires the recovery area to be enabled.
// Either enable the recovery area by setting the
// DB_RECOVERY_FILE_DEST and DB_RECOVERY_FILE_DEST_SIZE initialization
// parameters, or turn off flashback database with the
// ALTER DATABASE FLASHBACK OFF command.
So, Oracle
1. allows me to create a Restore Point
2. generates Flashback Log
3. confirms that they exist
BUT DOES NOT ALLOW ME TO FLASHBACK THE DATABASE.
DB_RECOVERY_FILE_DEST is still mandatory (even if you have ArchiveLogs being written elsewhere -- my ArchiveLogs were going to the default location under $ORACLE_HOME/dbs).
If you look at the documentation (column "Required" in Table 5-4) it does say that DB__RECOVERY_FILE_DEST is a required parameter -- although it doesnt explicitly say that this is required for the FLASHBACK LOGS. Also, my database was happy to generate ArchiveLogs in another, default, location ($ORACLE_HOME/dbs).
The CREATE RESTORE POINT command didn't give me any warning that the Restore Point would not be usable -- I would treat this as a Bug.
Categories: DBA Blogs