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Updated: 17 hours 23 min ago

Don’t go directly to Maximum Protection!

Mon, 2014-08-25 04:14

With a Data Guard Configuration in Maximum Performance protection mode, don’t go to Maximum Protection directly, because that leads to a restart of the primary database:

 Attention!

DGMGRL> show configuration;

Configuration - myconf

  Protection Mode: MaxPerformance
  Databases:
  prima  - Primary database
    physt  - Physical standby database
      physt2 - Physical standby database (receiving current redo)

Fast-Start Failover: DISABLED

Configuration Status:
SUCCESS

DGMGRL> edit configuration set protection mode as maxprotection;
Operation requires shutdown of instance "prima" on database "prima"
Shutting down instance "prima"...
Database closed.
Database dismounted.
ORACLE instance shut down.
Operation requires startup of instance "prima" on database "prima"
Starting instance "prima"...
ORACLE instance started.
Database mounted.
Database opened.

Instead, go to Maximum Availability first and then to Maximum Protection:

DGMGRL> edit configuration set protection mode as maxperformance;
Succeeded.
DGMGRL> edit configuration set protection mode as maxavailability;
Succeeded.
DGMGRL> edit configuration set protection mode as maxprotection;
Succeeded.

The demo was done with 12c, involving a cascading standby database, but the behavior is the same in 11g already. The odd thing about it is that DGMGRL will restart the primary without warning. Wanted to share that with the Oracle community for years but always got over it somehow.


Tagged: Data Guard, High Availability
Categories: DBA Blogs

Why Write-Through is still the default Flash Cache Mode on #Exadata X-4

Wed, 2014-08-06 12:41

The Flash Cache Mode still defaults to Write-Through on Exadata X-4 because most customers are better suited that way – not because Write-Back is buggy or unreliable. Chances are that Write-Back is not required, so we just save Flash capacity that way. So when you see this

CellCLI> list cell attributes flashcachemode
         WriteThrough

it is likely to your best :-)
Let me explain: Write-Through means that writing I/O coming from the database layer will first go to the spinning drives where it is mirrored according to the redundancy of the diskgroup where the file is placed that is written to. Afterwards, the cells may populate the Flash Cache if they think it will benefit subsequent reads, but there is no mirroring required. In case of hardware failure, the mirroring is already sufficiently done on the spinning drives, as the pictures shows:

Flash Cache Mode Write-Through

Flash Cache Mode WRITE-THROUGH

That changes with the Flash Cache Mode being Write-Back: Now writes go primarily to the Flashcards and popular objects may even never get aged out onto the spinning drives. At least that age out may happen significantly later, so the writes on flash must be mirrored now. The redundancy of the diskgroup where the object in question was placed on determines again the number of mirrored writes. The two pictures assume normal redundancy. In other words: Write-Back reduces the usable capacity of the Flashcache at least by half.

Flash Cache Mode Write-Back

Flash Cache Mode WRITE-BACK

Only databases with performance issues on behalf of writing I/O will benefit from Write-Back, the most likely symptom of which would be high numbers of the Free Buffer Waits wait-event. And Flash Logging is done with both Write-Through and Write-Back. So there is a good reason behind turning on the Write-Back Flash Cache Mode only on demand. I have explained this just very similar during my present Oracle University Exadata class in Frankfurt, by the way :-)


Tagged: exadata
Categories: DBA Blogs

Common Roles get copied upon plug-in with #Oracle Multitenant

Fri, 2014-08-01 08:51

What happens when you unplug a pluggable database that has local users who have been granted common roles? They get copied upon plug-in of the PDB to the target container database!

Before Unplug of the PDBThe picture above shows the situation before the unplug command. It has been implemented with these commands:

 

SQL> connect / as sysdba
Connected.
SQL> create role c##role container=all;

Role created.

SQL> grant select any table to c##role container=all;

Grant succeeded.

SQL> connect sys/oracle_4U@pdb1 as sysdba
Connected.
SQL> grant c##role to app;

Grant succeeded.



SQL> grant create session to app;

Grant succeeded.

The local user app has now been granted the common role c##role. Let’s assume that the application depends on the privileges inside the common role. Now the pdb1 is unplugged and plugged in to cdb2:

SQL> shutdown immediate
Pluggable Database closed.
SQL> connect / as sysdba
Connected.
SQL> alter pluggable database pdb1 unplug into '/home/oracle/pdb1.xml';

Pluggable database altered.

SQL> drop pluggable database pdb1;

Pluggable database dropped.

SQL> exit
Disconnected from Oracle Database 12c Enterprise Edition Release 12.1.0.1.0 - 64bit Production
With the Partitioning, OLAP, Advanced Analytics and Real Application Testing options
[oracle@EDE5R2P0 ~]$ . oraenv
ORACLE_SID = [cdb1] ? cdb2
The Oracle base for ORACLE_HOME=/u01/app/oracle/product/12.1.0/dbhome_1 is /u01/app/oracle
[oracle@EDE5R2P0 ~]$ sqlplus / as sysdba

SQL*Plus: Release 12.1.0.1.0 Production on Tue Jul 29 12:52:19 2014

Copyright (c) 1982, 2013, Oracle.  All rights reserved.


Connected to:
Oracle Database 12c Enterprise Edition Release 12.1.0.1.0 - 64bit Production
With the Partitioning, OLAP, Advanced Analytics and Real Application Testing options

SQL> create pluggable database pdb1 using '/home/oracle/pdb1.xml' nocopy;

Pluggable database created.

SQL> alter pluggable database pdb1 open;

Pluggable database altered.

SQL> connect app/app@pdb1
Connected.
SQL> select * from scott.dept;

    DEPTNO DNAME          LOC
---------- -------------- -------------
        10 ACCOUNTING     NEW YORK
        20 RESEARCH       DALLAS
        30 SALES          CHICAGO
        40 OPERATIONS     BOSTON

SQL> select * from session_privs;

PRIVILEGE
----------------------------------------
CREATE SESSION
SELECT ANY TABLE

SQL> connect / as sysdba
Connected.

SQL> select role,common from cdb_roles where role='C##ROLE';

ROLE
--------------------------------------------------------------------------------
COM
---
C##ROLE
YES

As seen above, the common role has been copied upon the plug-in like the picture illustrates:
After plug-in of the PDBNot surprisingly the local user app together with the local privilege CREATE SESSION was moved to the target container database. But it is not so obvious that the common role is copied then to the target CDB. This is something I found out during delivery of a recent Oracle University LVC about 12c New Features, thanks to a question of one attendee. My guess was it will lead to an error upon unplug, but this test-case proves it doesn’t. I thought that behavior may be of interest to the Oracle Community. As always: Don’t believe it, test it! :-)


Tagged: 12c New Features, Multitenant
Categories: DBA Blogs

Restore datafile from service: A cool #Oracle 12c Feature

Wed, 2014-07-02 09:02

You can restore a datafile directly from a physical standby database to the primary. Over the network. With compressed backupsets. How cool is that?

Here’s a demo from my present class Oracle Database 12c: Data Guard Administration. prima is the primary database on host01, physt is a physical standby database on host03. There is an Oracle Net configuration on both hosts that enable host01 to tnsping physt and host03 to tnsping prima

 

[oracle@host01 ~]$ rman target sys/oracle@prima

Recovery Manager: Release 12.1.0.1.0 - Production on Wed Jul 2 16:43:39 2014

Copyright (c) 1982, 2013, Oracle and/or its affiliates.  All rights reserved.

connected to target database: PRIMA (DBID=2084081935)

RMAN> run
{
set newname for datafile 4 to '/home/oracle/stage/users01.dbf';
restore (datafile 4 from service physt) using compressed backupset;
catalog datafilecopy '/home/oracle/stage/users01.dbf';
}

executing command: SET NEWNAME

Starting restore at 02-JUL-14
using target database control file instead of recovery catalog
allocated channel: ORA_DISK_1
channel ORA_DISK_1: SID=47 device type=DISK

channel ORA_DISK_1: starting datafile backup set restore
channel ORA_DISK_1: using compressed network backup set from service physt
channel ORA_DISK_1: specifying datafile(s) to restore from backup set
channel ORA_DISK_1: restoring datafile 00004 to /home/oracle/stage/users01.dbf
channel ORA_DISK_1: restore complete, elapsed time: 00:00:07
Finished restore at 02-JUL-14

cataloged datafile copy
datafile copy file name=/home/oracle/stage/users01.dbf RECID=8 STAMP=851877850

This does not require backups taken on the physical standby database.


Tagged: 12c New Features, Backup & Recovery, Data Guard
Categories: DBA Blogs

Data Guard 12c New Features: Far Sync & Real-Time Cascade

Wed, 2014-06-11 08:10

UKOUG Oracle Scene has published my article about two exciting Data Guard 12c New Features:

http://viewer.zmags.com/publication/62b883ad#/62b883ad/44

Far Sync Instance enables Zero-Data-Loss across large distance

Hope you find it useful :-)


Tagged: 12c New Features, Data Guard
Categories: DBA Blogs

Common Users & SYSDBA with #Oracle 12c Multitenancy

Wed, 2014-06-04 08:36

A 12c multitenant database introduces the new concept of local users and common users. This article shows simple use cases why DBAs may want to create common users – in contrast to the common users that are created automatically, like SYS, SYSTEM, MDSYS etc.

A typical requirement is to have a superuser other than SYS, but with the same power. Like the common user C##_SYS in the picture below.

Or suppose we have many pluggable databases (PDBs) and different superusers responsible for different PDBs like C##_ADMIN1 and C##_ADMIN2:

Common Users in Oracle 12cLet’s implement it as above. Initially, my demo environment looks like this:

 

SQL> select name,open_mode,con_id from v$pdbs;

NAME                           OPEN_MODE      CON_ID
------------------------------ ---------- ----------
PDB$SEED                       READ ONLY           2
PDB1                           READ WRITE          3
PDB2                           READ WRITE          4
PDB3                           READ WRITE          5

SQL> select * from v$pwfile_users;

USERNAME                       SYSDB SYSOP SYSAS SYSBA SYSDG SYSKM     CON_ID
------------------------------ ----- ----- ----- ----- ----- ----- ----------
SYS                            TRUE  TRUE  FALSE FALSE FALSE FALSE          0
SYSDG                          FALSE FALSE FALSE FALSE TRUE  FALSE          1
SYSBACKUP                      FALSE FALSE FALSE TRUE  FALSE FALSE          1
SYSKM                          FALSE FALSE FALSE FALSE FALSE TRUE           1

At first, I create C##_SYS and grant SYSDBA as a common privilege to that new user:

SQL> create user c##_sys identified by oracle container=all;

User created.

SQL> grant sysdba to c##_sys container=all;

Grant succeeded.

SQL> select * from v$pwfile_users;

USERNAME                       SYSDB SYSOP SYSAS SYSBA SYSDG SYSKM     CON_ID
------------------------------ ----- ----- ----- ----- ----- ----- ----------
SYS                            TRUE  TRUE  FALSE FALSE FALSE FALSE          0
SYSDG                          FALSE FALSE FALSE FALSE TRUE  FALSE          1
SYSBACKUP                      FALSE FALSE FALSE TRUE  FALSE FALSE          1
SYSKM                          FALSE FALSE FALSE FALSE FALSE TRUE           1
C##_SYS                        TRUE  FALSE FALSE FALSE FALSE FALSE          0

C##_SYS can now do anything to any PDB:

SQL> connect c##_sys/oracle@edd2r6p0/pdb1 as sysdba
Connected.
SQL> shutdown immediate
Pluggable Database closed.
SQL> connect / as sysdba
Connected.
SQL> select name,open_mode,con_id from v$pdbs;

NAME                           OPEN_MODE      CON_ID
------------------------------ ---------- ----------
PDB$SEED                       READ ONLY           2
PDB1                           MOUNTED             3
PDB2                           READ WRITE          4
PDB3                           READ WRITE          5

SQL> connect c##_sys/oracle@edd2r6p0/pdb1 as sysdba
Connected.
SQL> startup
Pluggable Database opened.
SQL> connect / as sysdba
Connected.
SQL> select name,open_mode,con_id from v$pdbs;

NAME                           OPEN_MODE      CON_ID
------------------------------ ---------- ----------
PDB$SEED                       READ ONLY           2
PDB1                           READ WRITE          3
PDB2                           READ WRITE          4
PDB3                           READ WRITE          5

Notice that there is a subtle difference in granting SYSDBA of the container database (CDB) as local or common privilege:

SQL> revoke sysdba from c##_sys container=all;

Revoke succeeded.

SQL> grant sysdba to c##_sys;

Grant succeeded.

SQL> select * from v$pwfile_users;

USERNAME                       SYSDB SYSOP SYSAS SYSBA SYSDG SYSKM     CON_ID
------------------------------ ----- ----- ----- ----- ----- ----- ----------
SYS                            TRUE  TRUE  FALSE FALSE FALSE FALSE          0
SYSDG                          FALSE FALSE FALSE FALSE TRUE  FALSE          1
SYSBACKUP                      FALSE FALSE FALSE TRUE  FALSE FALSE          1
SYSKM                          FALSE FALSE FALSE FALSE FALSE TRUE           1
C##_SYS                        TRUE  FALSE FALSE FALSE FALSE FALSE          1

SQL> connect c##_sys/oracle@edd2r6p0/pdb1 as sysdba
ERROR:
ORA-01031: insufficient privileges


Warning: You are no longer connected to ORACLE.

C##_SYS has SYSDBA of the CDB “only”, therefore the error. Although:

SQL> connect c##_sys/oracle as sysdba
Connected.
SQL> show con_name

CON_NAME
------------------------------
CDB$ROOT
SQL> alter session set container=pdb1;

Session altered.

SQL> shutdown immediate
Pluggable Database closed.
SQL> show con_name

CON_NAME
------------------------------
PDB1
SQL> startup
Pluggable Database opened.
SQL> connect c##_sys/oracle as sysdba
Connected.
SQL> select name,open_mode,con_id from v$pdbs;

NAME                           OPEN_MODE      CON_ID
------------------------------ ---------- ----------
PDB$SEED                       READ ONLY           2
PDB1                           READ WRITE          3
PDB2                           READ WRITE          4
PDB3                           READ WRITE          5

However, the proper way is probably granting it as a common privilege:

SQL> revoke sysdba from c##_sys;

Revoke succeeded.

SQL> grant sysdba to c##_sys container=all;

Grant succeeded.

Now to the implementation of C##_ADMIN1 and C##_ADMIN2. The point is here, that SYSDBA can be granted as a local privilege for certain PDBs only, to the effect that different superusers can be responsible for different groups of PDBs:

SQL> create user c##_admin1 identified by oracle container=all;

User created.

SQL> alter session set container=pdb1;

Session altered.

SQL> grant sysdba to c##_admin1 container=current;

Grant succeeded.

SQL> connect / as sysdba
Connected.
SQL> select * from v$pwfile_users;

USERNAME                       SYSDB SYSOP SYSAS SYSBA SYSDG SYSKM     CON_ID
------------------------------ ----- ----- ----- ----- ----- ----- ----------
SYS                            TRUE  TRUE  FALSE FALSE FALSE FALSE          0
SYSDG                          FALSE FALSE FALSE FALSE TRUE  FALSE          1
SYSBACKUP                      FALSE FALSE FALSE TRUE  FALSE FALSE          1
SYSKM                          FALSE FALSE FALSE FALSE FALSE TRUE           1
C##_SYS                        TRUE  FALSE FALSE FALSE FALSE FALSE          0
C##_ADMIN1                     TRUE  FALSE FALSE FALSE FALSE FALSE          3

6 rows selected.

For now, C##_ADMIN1 can only connect to PDB1:

SQL> connect c##_admin1/oracle@edd2r6p0/pdb1 as sysdba
Connected.
SQL> select count(*) from session_privs;

  COUNT(*)
----------
       233

SQL> connect c##_admin1/oracle@edd2r6p0/pdb2 as sysdba
ERROR:
ORA-01017: invalid username/password; logon denied


Warning: You are no longer connected to ORACLE.

The completed implementation of the picture above:

SQL> connect / as sysdba
Connected.
SQL> alter session set container=pdb2;

Session altered.

SQL> grant sysdba to c##_admin1 container=current;

Grant succeeded.

SQL> connect / as sysdba
Connected.
SQL> create user c##_admin2 identified by oracle;

User created.

SQL> alter session set container=pdb3;

Session altered.

SQL> grant sysdba to c##_admin2 container=current;

Grant succeeded.

SQL> connect / as sysdba
Connected.
SQL> select * from v$pwfile_users;

USERNAME                       SYSDB SYSOP SYSAS SYSBA SYSDG SYSKM     CON_ID
------------------------------ ----- ----- ----- ----- ----- ----- ----------
SYS                            TRUE  TRUE  FALSE FALSE FALSE FALSE          0
SYSDG                          FALSE FALSE FALSE FALSE TRUE  FALSE          1
SYSBACKUP                      FALSE FALSE FALSE TRUE  FALSE FALSE          1
SYSKM                          FALSE FALSE FALSE FALSE FALSE TRUE           1
C##_SYS                        TRUE  FALSE FALSE FALSE FALSE FALSE          0
C##_ADMIN1                     TRUE  FALSE FALSE FALSE FALSE FALSE          3
C##_ADMIN1                     TRUE  FALSE FALSE FALSE FALSE FALSE          4
C##_ADMIN2                     TRUE  FALSE FALSE FALSE FALSE FALSE          5

8 rows selected.

The whole example is from my present 12c New Features in Düsseldorf, by the way. Hope you find it useful :-)
As always: Don’t believe it, test it!


Tagged: 12c New Features
Categories: DBA Blogs

HA of Database Control for RAC made easy

Mon, 2014-05-19 09:11

When you install an 11g RAC database without Grid Control respectively Cloud Control present, this is what the DBCA will give you:

RAC_dbconsole1There is one Database Control OC4J Container only, running on host01. Should host01 go down, the Enterprise Manager is no longer available now. We could make that a resource, known to the clusterware and let it failover in that case. But also – and even easier – we can start a second OC4J Container to run on host02 simultaneously like this:

RAC_dbconsole2Let’s see how to implement that:

 

[oracle@host01 ~]$ emca -reconfig dbcontrol -cluster -EM_NODE host02 -EM_NODE_LIST host02

STARTED EMCA at May 14, 2014 5:16:14 PM
EM Configuration Assistant, Version 11.2.0.3.0 Production
Copyright (c) 2003, 2011, Oracle.  All rights reserved.

Enter the following information:
Database unique name: orcl
Service name: orcl
Do you wish to continue? [yes(Y)/no(N)]: yes
May 14, 2014 5:16:26 PM oracle.sysman.emcp.EMConfig perform
INFO: This operation is being logged at /u01/app/oracle/cfgtoollogs/emca/orcl/emca_2014_05_14_17_16_14.log.
May 14, 2014 5:16:29 PM oracle.sysman.emcp.util.DBControlUtil stopOMS
INFO: Stopping Database Control (this may take a while) ...
May 14, 2014 5:16:34 PM oracle.sysman.emcp.EMAgentConfig performDbcReconfiguration
INFO: Propagating /u01/app/oracle/product/11.2.0/dbhome_1/host02_orcl/sysman/config/emd.properties to remote nodes ...
May 14, 2014 5:16:34 PM oracle.sysman.emcp.util.DBControlUtil startOMS
INFO: Starting Database Control (this may take a while) ...
May 14, 2014 5:17:33 PM oracle.sysman.emcp.EMDBPostConfig performDbcReconfiguration
INFO: Database Control started successfully
May 14, 2014 5:17:34 PM oracle.sysman.emcp.EMDBPostConfig showClusterDBCAgentMessage
INFO:
****************  Current Configuration  ****************
 INSTANCE            NODE           DBCONTROL_UPLOAD_HOST
----------        ----------        ---------------------

orcl              host01              host01.example.com
orcl              host02              host02.example.com

Enterprise Manager configuration completed successfully
FINISHED EMCA at May 14, 2014 5:17:34 PM
[oracle@host01 ~]$ emctl status dbconsole
Oracle Enterprise Manager 11g Database Control Release 11.2.0.3.0
Copyright (c) 1996, 2011 Oracle Corporation.  All rights reserved.

https://host01.example.com:1158/em/console/aboutApplication

Oracle Enterprise Manager 11g is running.
------------------------------------------------------------------
Logs are generated in directory /u01/app/oracle/product/11.2.0/dbhome_1/host01_orcl/sysman/log

Not only can I access Database Control at host01 as usual, I can also get it at host02 now:

[oracle@host01 ~]$ ssh host02
Last login: Wed May 14 10:50:32 2014 from host01.example.com
[oracle@host02 ~]$ emctl status dbconsole
Oracle Enterprise Manager 11g Database Control Release 11.2.0.3.0
Copyright (c) 1996, 2011 Oracle Corporation.  All rights reserved.
https://host02.example.com:1158/em/console/aboutApplication
Oracle Enterprise Manager 11g is running.
------------------------------------------------------------------
Logs are generated in directory /u01/app/oracle/product/11.2.0/dbhome_1/host02_orcl/sysman/log

All this is of course not new, but you won’t find it easy in the docs. That is something from my RAC accelerated course last week in Reading, by the way. Even seasoned RAC DBAs are sometimes not aware of that option, so I thought it might be helpful to publish it here briefly :-)


Tagged: Database Control, High Availability, Oracle Enterprise Manager, RAC
Categories: DBA Blogs

Consider speaking at #ukoug_tech14

Thu, 2014-05-15 10:11

The call for papers is still open for UKOUG Tech 14 – a great event to speak at for sure!

UKOUG Tech 14The board explicitly encourages first-time speakers and women to submit an abstract.

Both doesn’t apply for me, but I have submitted abstracts in spite :-)

I can say only the best about the past annual conferences of the UK Oracle User Group. Great speakers, very good conditions and an excellent opportunity to get in touch with other Oracle enthusiasts.

So if you – yes, YOU! – are an expert in Oracle Core Technology, but hesitated so far to speak at public events about your topics, this might be the best time to get over it :-)


Tagged: #ukoug_tech14
Categories: DBA Blogs