It looks like we hit 13930580 on one of our systems and I wanted to put some example output showing log file sync times going above 10 milliseconds (10,000 microseconds) after the log writer switches to polling.
Here is the output in the lgwr trace file showing the switch to polling:
*** 2013-12-27 01:50:47.374 kcrfw_update_adaptive_sync_mode: post->poll long#=1 sync#=1 sync=55336 poll=1913 4 rw=5506 rw+=5506 ack=0 min_sleep=19134 *** 2013-12-27 01:50:47.374 Log file sync switching to polling Current scheduling delay is 1 usec Current approximate redo synch write rate is 0 per sec
Here is a report showing the number of log file sync waits and their average time in microseconds:
END_INTERVAL_TIME number of waits ave microseconds -------------------------- --------------- ---------------- 26-DEC-13 03.00.19.333 PM 976539 2279.06861 26-DEC-13 04.00.43.475 PM 681212 2029.32406 26-DEC-13 05.00.07.975 PM 343932 1575.26284 26-DEC-13 06.00.34.772 PM 163911 1850.74354 26-DEC-13 07.01.00.911 PM 73151 3815.28597 26-DEC-13 08.00.24.463 PM 39304 5038.05427 26-DEC-13 09.00.48.970 PM 32122 5677.00557 26-DEC-13 10.00.13.491 PM 472349 2353.95857 26-DEC-13 11.00.40.521 PM 18679 18655.5294 27-DEC-13 12.00.06.276 AM 19618 17046.2287 27-DEC-13 01.00.30.299 AM 18983 5721.99178 27-DEC-13 02.00.54.261 AM 17724 17106.3415 27-DEC-13 03.00.18.282 AM 9088 25342.7271 27-DEC-13 04.00.42.218 AM 14365 12128.7 27-DEC-13 05.00.06.391 AM 16323 12879.8831 27-DEC-13 06.00.31.379 AM 43758 15326.7298 27-DEC-13 07.00.56.027 AM 83819 14796.2851 27-DEC-13 08.00.20.637 AM 168718 13506.4363 27-DEC-13 09.00.47.262 AM 302827 19116.9491 27-DEC-13 10.00.14.014 AM 480347 19358.6655 27-DEC-13 11.00.41.178 AM 512777 15952.2358 27-DEC-13 12.00.08.220 PM 511091 13799.5512 27-DEC-13 01.00.38.131 PM 576341 10183.4347 27-DEC-13 02.00.06.308 PM 524568 10251.1259
Notice how the average wait time goes above 10,000 microseconds consistently once the log writer switches to polling between 1 and 2 am on 12/27/2013. I didn’t show all the output but this long log file sync wait time has continued since the switch.
Also, these long log file sync times don’t correspond to long log file parallel write times. Here are the number and averages of log file parallel write waits for the same time frame:
END_INTERVAL_TIME number of waits ave microseconds -------------------------- --------------- ---------------- 26-DEC-13 03.00.19.333 PM 902849 1426.66601 26-DEC-13 04.00.43.475 PM 659701 1394.87763 26-DEC-13 05.00.07.975 PM 344245 1294.92401 26-DEC-13 06.00.34.772 PM 166643 1586.64944 26-DEC-13 07.01.00.911 PM 80457 4019.29429 26-DEC-13 08.00.24.463 PM 46409 5580.67827 26-DEC-13 09.00.48.970 PM 69218 5115.20904 26-DEC-13 10.00.13.491 PM 475297 2219.80541 26-DEC-13 11.00.40.521 PM 40943 19405.052 27-DEC-13 12.00.06.276 AM 38835 18160.8073 27-DEC-13 01.00.30.299 AM 24734 6321.38425 27-DEC-13 02.00.54.261 AM 33617 11723.6698 27-DEC-13 03.00.18.282 AM 36469 17485.2614 27-DEC-13 04.00.42.218 AM 19344 6955.27042 27-DEC-13 05.00.06.391 AM 17857 4399.75718 27-DEC-13 06.00.31.379 AM 45098 4923.02763 27-DEC-13 07.00.56.027 AM 83700 3610.39713 27-DEC-13 08.00.20.637 AM 160919 2841.31507 27-DEC-13 09.00.47.262 AM 266405 3523.86855 27-DEC-13 10.00.14.014 AM 384795 3367.5075 27-DEC-13 11.00.41.178 AM 437806 2729.84248 27-DEC-13 12.00.08.220 PM 448261 2442.81012 27-DEC-13 01.00.38.131 PM 511648 1880.74418 27-DEC-13 02.00.06.308 PM 481106 1919.21158
The average I/O time – log file parallel write – is pretty low when the system is active (more than 100,000 waits per hour) – usually less than 4000 microseconds and yet log file sync is always more than 10,000 after the switch to polling. Also, the CPU on the system is consistently less than 30% used so it isn’t a system load issue.
Here are some Oracle support documents related to this issue:
Adaptive Switching Between Log Write Methods can Cause 'log file sync' Waits (Doc ID 1462942.1) Waits for "log file sync" with Adaptive Polling vs Post/Wait Choice Enabled (Doc ID 1541136.1) Bug 13930580: LGWR IS BLOCKING SESSIONS
Here is the script I used to get the wait output:
set linesize 32000 set pagesize 1000 set long 2000000000 set longchunksize 1000 set head off; set verify off; set termout off; column u new_value us noprint; column n new_value ns noprint; select name n from v$database; select user u from dual; set sqlprompt &ns:&us> set head on set echo on set termout on set trimspool on UNDEFINE WAITNAME UNDEFINE MINIMUMWAITS spool "&ns.&&WAITNAME..log" column END_INTERVAL_TIME format a26 select sn.END_INTERVAL_TIME, (after.total_waits-before.total_waits) "number of waits", (after.time_waited_micro-before.time_waited_micro)/ (after.total_waits-before.total_waits) "ave microseconds", before.event_name "wait name" from DBA_HIST_SYSTEM_EVENT before, DBA_HIST_SYSTEM_EVENT after, DBA_HIST_SNAPSHOT sn where before.event_name='&&WAITNAME' and after.event_name=before.event_name and after.snap_id=before.snap_id+1 and after.instance_number=1 and before.instance_number=after.instance_number and after.snap_id=sn.snap_id and after.instance_number=sn.instance_number and (after.total_waits-before.total_waits) > &&MINIMUMWAITS order by after.snap_id; spool off
I gave log file sync as the WAITNAME and 1 as MINIMUMWAITS for the first output. I changed WAITNAME to log file parallel write for the second one with 1 still for MINIMUMWAITS.
It looks like there is a new feature in 11.2 that was finally turned on by default in 184.108.40.206. The work around is to set a hidden parameter to false to turn off the new feature. Check out the Oracle support docs I listed for details.
p.s. I forgot to mention that when I tested on a test database with and without this new feature the log file sync times were lower with the new feature, as they should be.
With _use_adaptive_log_file_sync=TRUE (feature enabled):
Top 5 Timed Foreground EventsEvent Waits Time(s) Avg wait (ms) % DB time Wait Class log file sync 639,598 3,466 5 86.74 Commit DB CPU 397 9.93 buffer exterminate 683 14 21 0.36 Other virtual circuit wait 912 12 13 0.31 Network SQL*Net message to client 1,293,196 7 0 0.17 Network
With _use_adaptive_log_file_sync=FALSE (disabled as in earlier versions of 11.2):
Top 5 Timed Foreground EventsEvent Waits Time(s) Avg wait (ms) % DB time Wait Class log file sync 639,644 3,553 6 87.31 Commit DB CPU 367 9.02 buffer exterminate 1,364 28 21 0.69 Other buffer busy waits 2,679 15 6 0.37 Concurrency virtual circuit wait 903 13 15 0.32 Network
With the new feature enabled log file sync was 5 milliseconds instead of 6 without it. So, the new feature does speed up log file sync waits when it is working normally. But, there must be some bug condition where it degrades to greater than 10 millisecond log file syncs.
We have an incredible set of people doing workshops for our attendees. We are working on finalizing a fourth workshop in the Essbase area but not quite ready to announce that on.
We are going to go live this weekend with the ability to register for our latest addition to the workshops.
From Relational to Hadoop - Migrating your data pipelineI am very excited to announce this addition!
Will update this post with links when this workshop is online for registration.
Another Oozie tip blog post.
If you try to use Sqoop action in Oozie, you know you can use the “command” format, with the entire Sqoop configuration in a single line:
<pre><workflow-app name="sample-wf" xmlns="uri:oozie:workflow:0.1"> ... <action name="myfirsthivejob"> <sqoop xmlns="uri:oozie:sqoop-action:0.2"> <job-traker>foo:8021</job-tracker> <name-node>bar:8020</name-node> <command>import --connect jdbc:hsqldb:file:db.hsqldb --table TT --target-dir hdfs://localhost:8020/user/tucu/foo -m 1</command> </sqoop> <ok to="myotherjob"/> <error to="errorcleanup"/> </action> ... </workflow-app>
This is convenient, but can be difficult to read and maintain. I prefer using the “arg” syntax, with each argument in its own line:
<workflow-app name="sample-wf" xmlns="uri:oozie:workflow:0.1"> ... <action name="myfirsthivejob"> <sqoop xmlns="uri:oozie:sqoop-action:0.2"> <job-traker>foo:8021</job-tracker> <name-node>bar:8020</name-node> <arg>import</arg> <arg>--connect</arg> <arg>jdbc:hsqldb:file:db.hsqldb</arg> <arg>--table</arg> <arg>TT</arg> <arg>--target-dir</arg> <arg>hdfs://localhost:8020/user/tucu/foo</arg> <arg>-m</arg> <arg>1</arg> </sqoop> <ok to="myotherjob"/> <error to="errorcleanup"/> </action> ... </workflow-app>
As you can see, each argument here is in its own “arg” tag. Even two arguments that belong together like “–table” and “TT” go in two separate tags.
If you’ll try to put them together for readability, as I did, Sqoop will throw its entire user manual at you. It took me a while to figure out why this is an issue.
When you call Oozie from the command line, all the arguments you pass are sent as a String array, and the spaces separate the arguments into array elements. So if you call Sqoop with “–table TT” it will be two elements, “–table” and “TT”.
When using “arg” tags in Oozie, you are basically generating the same array in XML. Oozie will turn the XML argument list into an array and pass it to Sqoop just the way it would in the command line. Then Sqoop parses it in exactly the same way.
So every item separated with space in the command line must be in separate tags in Oozie.
Its simple and logical once you figure out why :)
If you want to dig a bit more into how Sqoop parses its arguments, it is using Apache Commons CLI with GnuParser. You can read all about it.
Just got off of a Webex with Delphix support. They upgraded our Delphix server from version 220.127.116.11 to 18.104.22.168. It took about twenty minutes. Pretty nice compared to an Oracle database upgrade I think!
The only thing that took some time was that I had to be sure I had enough space. It looks like Delphix needs your disk space to be no more than 85% utilized to fully function. We ended up extending our four 1.5 terabyte luns to 1.9 TB each to give us space. Then I cleaned up some archive log space by running a snapsync on each source database to completion. Our system just needed a little TLC to get some space free again.
But, the upgrade itself, running the scripts and rebooting the server, took 20 minutes and was all done by Delphix support for no extra charge. Sweet.
In March 2012, I put together a blog post entitled Disabling Oracle triggers on a per-session basis, outlining a way to suspend trigger execution for the current session through a PL/SQL call. Commenter Bryan posted a comment saying he couldn’t get it working in 22.214.171.124:
Unfortunately Oracle seems to have disabled this use in 126.96.36.199, and most likely 12.1 as well. Boo-Hiss! This is needed functionality for DBAs!A new parameter: enable_goldengate_replication
I tried this on an Oracle 188.8.131.52 system, and I indeed got an error:
SQL> exec sys.dbms_xstream_gg.set_foo_trigger_session_contxt(fire=>true); BEGIN sys.dbms_xstream_gg.set_foo_trigger_session_contxt(fire=>true); END; * ERROR at line 1: ORA-26947: Oracle GoldenGate replication is not enabled. ORA-06512: at "SYS.DBMS_XSTREAM_GG_INTERNAL", line 46 ORA-06512: at "SYS.DBMS_XSTREAM_GG", line 13 ORA-06512: at line 1
A quick look at
oerr gives a path forward, assuming you do indeed have a GoldenGate license:
[oracle@ora11gr2b ~]$ oerr ora 26947 26947, 00000, "Oracle GoldenGate replication is not enabled." // *Cause: The 'enable_goldengate_replication' parameter was not set to 'true'. // *Action: Set the 'enable_goldengate_replication' parameter to 'true' // and retry the operation. // Oracle GoldenGate license is needed to use this parameter.
The Oracle reference gives a bit more info
ENABLE_GOLDENGATE_REPLICATION controls services provided by the RDBMS for Oracle GoldenGate (both capture and apply services). Set this to true to enable RDBMS services used by Oracle GoldenGate.
The RDBMS services controlled by this parameter also include (but are not limited to):
Service to suppress triggers used by GoldenGate Replicat
As do the GoldenGate 12.1.2 docs:
The database services required to support Oracle GoldenGate capture and apply must be enabled explicitly for an Oracle 184.108.40.206 database. This is required for all modes of Extract and Replicat.
To enable Oracle GoldenGate, set the following database initialization parameter. All instances in Oracle RAC must have the same setting.
So here goes nothing:
SQL> alter system set enable_goldengate_replication=true; System altered. SQL> exec sys.dbms_xstream_gg.set_foo_trigger_session_contxt(fire=>true); BEGIN sys.dbms_xstream_gg.set_foo_trigger_session_contxt(fire=>true); END; * ERROR at line 1: ORA-01031: insufficient privileges ORA-06512: at "SYS.DBMS_XSTREAM_GG_INTERNAL", line 46 ORA-06512: at "SYS.DBMS_XSTREAM_GG", line 13 ORA-06512: at line 1
Another error: missing privileges. I checked and double-checked that the required GoldenGate privileges were indeed assigned.Tracing and permission checks
It’s time to run a 100046 trace (SQL trace) to see what’s really going on.
SQL> alter session set events '10046 trace name context forever, level 12'; Session altered. SQL> exec sys.dbms_xstream_gg.set_foo_trigger_session_contxt(fire=>true); BEGIN sys.dbms_xstream_gg.set_foo_trigger_session_contxt(fire=>true); END; * ERROR at line 1: ORA-01031: insufficient privileges ORA-06512: at "SYS.DBMS_XSTREAM_GG_INTERNAL", line 46 ORA-06512: at "SYS.DBMS_XSTREAM_GG", line 13 ORA-06512: at line 1
And tracefile does show some interesting information. A few of the more interesting snippets:
PARSING IN CURSOR #140324121137184 len=76 dep=0 uid=91 oct=47 lid=91 tim=1388531465245781 hv=1323338123 ad='6c1f63a0' sqlid='gvq73797f12cb' BEGIN sys.dbms_xstream_gg.set_foo_trigger_session_contxt(fire=>true); END; END OF STMT ... PARSING IN CURSOR #140324121064984 len=187 dep=1 uid=0 oct=3 lid=0 tim=1388531465246387 hv=2028900049 ad='6c128db8' sqlid='aa9h2ajwfx3qj' SELECT COUNT(*) FROM ( SELECT GP.USERNAME FROM DBA_GOLDENGATE_PRIVILEGES GP WHERE GP.USERNAME = :B1 UNION ALL SELECT GRANTEE FROM DBA_ROLE_PRIVS WHERE GRANTEE=:B1 AND GRANTED_ROLE='DBA' ) END OF STMT ... Bind#0 ... value="GGS" ... Bind#1 ... value="GGS" ...
The SQL statement is actually checking two things. The first is looking for the current username in the
dba_goldengate_privileges view. This view isn’t listed in the Oracle 11.2 documentation, but it does appear in the 12c docs:
ALL_GOLDENGATE_PRIVILEGES displays details about Oracle GoldenGate privileges for the user.
Oracle GoldenGate privileges are granted using the DBMS_GOLDENGATE_AUTH package.
DBA_GOLDENGATE_PRIVILEGES displays details about Oracle GoldenGate privileges for all users who have been granted Oracle GoldenGate privileges.
USER_GOLDENGATE_PRIVILEGES displays details about Oracle GoldenGate privileges. This view does not display the USERNAME column.
I had previously run
dbms_goldengate_auth to grant privs here, so should be OK.
The second check simply verifies that the
DBA role had been granted to the current user, again as recommended by the documentation. (A side note: in previous versions, I had avoided granting the overly broad DBA role to the GoldenGate user in favor of specific grants for the objects it uses. There’s no reason for the GoldenGate user to need to read and modify data objects that aren’t related to its own replication activities for example. And I would argue that it helps avoid errors such as putting the wrong schema in a map statement when permissions are restricted. But sadly it’s no longer possible in the world of 220.127.116.11.)
Running the query manually to verify that the grants are indeed in place:
SQL> SELECT COUNT(*) FROM ( SELECT GP.USERNAME FROM DBA_GOLDENGATE_PRIVILEGES GP WHERE GP.USERNAME = 'GGS' UNION ALL SELECT GRANTEE FROM DBA_ROLE_PRIVS WHERE GRANTEE='GGS' AND GRANTED_ROLE='DBA' ); COUNT(*) ---------- 2
Looks good, so that doesn’t seem to be the problem.Tracing #2: system properties
Back to the 10046 tracefile:
PARSING IN CURSOR #140324119717656 len=45 dep=1 uid=0 oct=3 lid=0 tim=1388531465253124 hv=3393782897 ad='78ae2b40' sqlid='9p6bq1v54k13j' select value$ from sys.props$ where name = :1 END OF STMT ... Bind#0 ... value="GG_XSTREAM_FOR_STREAMS" ... FETCH #140324119717656:c=0,e=44,p=0,cr=2,cu=0,mis=0,r=0,dep=1,og=1,plh=415205717,tim=1388531465254441
Because this SQL statement involves an ordinary
select without an aggregate function, I can look at the
FETCH line in the tracefile to get the number of rows returned. In this case it’s
r=0, meaning no rows returned.
The query itself is looking for a system property I haven’t seen before: GG_XSTREAM_FOR_STREAMS. A Google search returns only a single result: the PDF version of the Oracle 11.2 XStream guide. Quoting:
This procedure enables XStream capabilities and performance optimizations for Oracle
This procedure is intended for users of Oracle Streams who want to enable XStream
capabilities and optimizations. For example, you can enable the optimizations for an
Oracle Streams replication configuration that uses capture processes and apply
processes to replicate changes between Oracle databases.
These capabilities and optimizations are enabled automatically for XStream
components, such as outbound servers, inbound servers, and capture processes that
send changes to outbound servers. It is not necessary to run this procedure for
When XStream capabilities are enabled, Oracle Streams components can stream ID key
LCRs and sequence LCRs. The XStream performance optimizations improve efficiency
in various areas, including:
? LCR processing
? Handling large transactions
? DML execution during apply
? Dependency computation and scheduling
? Capture process parallelism
On the surface, I don’t see what this would have to do with trigger execution, but I’m going to try enabling it as per the newly read document anyway:
SQL> exec dbms_xstream_adm.ENABLE_GG_XSTREAM_FOR_STREAMS(enable=>true); PL/SQL procedure successfully completed. SQL> exec sys.dbms_xstream_gg.set_foo_trigger_session_contxt(fire=>true); BEGIN sys.dbms_xstream_gg.set_foo_trigger_session_contxt(fire=>true); END; * ERROR at line 1: ORA-01031: insufficient privileges ORA-06512: at "SYS.DBMS_XSTREAM_GG_INTERNAL", line 46 ORA-06512: at "SYS.DBMS_XSTREAM_GG", line 13 ORA-06512: at line 1
No dice.Tracing #3: process names
Onto the next SQL in the tracefile:
PARSING IN CURSOR #140324120912848 len=114 dep=1 uid=0 oct=3 lid=0 tim=1388531465255628 hv=1670585998 ad='6c2d6098' sqlid='a9mwtndjt67nf' SELECT COUNT(*) FROM V$SESSION S, V$PROCESS P WHERE P.ADDR = S.PADDR AND S.PROGRAM LIKE 'extract%' AND p.spid = :1 END OF STMT ... Bind#0 ... value="2293"
Now we look in v$session, to see if a session associated with the process with OS PID 2293 (which happens to be the SPID of our current shadow process) has a PROGRAM column starting with the word extract. extract is, naturally, the name of the GoldenGate executable that captures data from the source system. In a GoldenGate system, however, trigger suppression does not happen in the extract process at all, but rather the replicat process that applies changes on the target system. So I’m going to skip this check and move on to the next one in the tracefile:
PARSING IN CURSOR #140324120905624 len=169 dep=1 uid=0 oct=3 lid=0 tim=1388531465257346 hv=3013382849 ad='6c122b38' sqlid='38pkvxattt4q1' SELECT COUNT(*) FROM V$SESSION S, V$PROCESS P WHERE P.ADDR = S.PADDR AND (S.MODULE LIKE 'OGG%' OR S.MODULE = 'GoldenGate') AND S.PROGRAM LIKE 'replicat%' AND p.spid = :1 END OF STMT ... Bind#0 ... value="2293"
This SQL is similar to the previous one, but instead of looking for a program called
extract, it looks for one called
replicat, and adds an extra check, so see if the
module column either starts with
OGG or is called
GoldenGate. And since it’s the
replicat process that does trigger disabling in GoldenGate, this check is likely to be related.
To make this check succeed, I’m going to have to change both the
module columns in v$session for the current session. of the two,
module is much easier to modify: a single call to dbms_application_info.set_module. But modifying
program is less straightforward. One approach is to use Java code with Oracle’s JDBC Thin driver and setting the aptly-named
v$session.program property, as explained in De Roeptoeter. But I’m hoping to stay with something I can do in SQL*Plus. If you’ve looked through a packet trace of a SQL*Net connection being established, you will know that the program name is passed by the client at the time of connection establishment, so could be modified by either modifying the network packet in transit. This is also complex to get working, as it also involves fixing checksums and the like. There’s a post on Slavik’s blog with a sample OCI C program that modifies its program information. Again more complexity thn I’d like, but it gave me an idea: if the
program is populated by the name of the client-side executable, why don’t we simply copy sqlplus to a name that the
dbms_xstream_gg likes better?
[oracle@ora11gr2b ~]$ cp $ORACLE_HOME/bin/sqlplus ./replicat [oracle@ora11gr2b ~]$ ./replicat ggs SQL*Plus: Release 18.104.22.168.0 Production on Mon Dec 30 14:09:05 2013 Copyright (c) 1982, 2013, Oracle. All rights reserved. Enter password: Connected to: Oracle Database 11g Enterprise Edition Release 22.214.171.124.0 - 64bit Production With the Partitioning, OLAP, Data Mining and Real Application Testing options SQL> exec dbms_application_info.set_module('OGG',''); PL/SQL procedure successfully completed. SQL> exec sys.dbms_xstream_gg.set_foo_trigger_session_contxt(fire=>true); PL/SQL procedure successfully completed.
So it looks like you can disable triggers per-session in 126.96.36.199 just like previous versions, but need to jump through a few more hoops to do it. A few conclusions to draw:
- Oracle patchsets, while normally intended to include bugfixes, can have major changes to underlying functionality too. See Jeremy Schneider’s post on adaptive log file sync for an even more egregious example. So before applying a patchset, test thoroughly!
- The enforcement of full DBA privileges for the GoldenGate user in Oracle 188.8.131.52 requires very broad permissions to use GoldenGate, which can be a concern in security-conscious or consolidated environments.
TL;DR: Yes you can still disable triggers per-session in Oracle 184.108.40.206, but you have to have a GoldenGate license, set the
enable_goldengate_replication parameter, use a program name that starts with
replicat, and set your module to
As an enhancement to the Oracle Database whoami for versions before 12c, this also shows the Container Name to which the session is connected:
[oracle@linuxbox ~]$ sqlplus / as sysdba SQL*Plus: Release 220.127.116.11.0 Production on Wed Jan 8 12:34:04 2014 Copyright (c) 1982, 2013, Oracle. All rights reserved. Connected to: Oracle Database 12c Enterprise Edition Release 18.104.22.168.0 - 64bit Production With the Partitioning, OLAP, Advanced Analytics and Real Application Testing options SQL> @whoami USER: SYS SESSION ID: 253 CURRENT_SCHEMA: SYS INSTANCE NAME: cdb1 CDB NAME: cdb1 CONTAINER NAME: CDB$ROOT DATABASE ROLE: PRIMARY OS USER: oracle CLIENT IP ADDRESS: SERVER HOSTNAME: linuxbox CLIENT HOSTNAME: linuxbox PL/SQL procedure successfully completed. SQL> connect system/oracle_4U@pdb1 Connected. SQL> @whoami USER: SYSTEM SESSION ID: 253 CURRENT_SCHEMA: SYSTEM INSTANCE NAME: cdb1 CDB NAME: cdb1 CONTAINER NAME: PDB1 DATABASE ROLE: PRIMARY OS USER: oracle CLIENT IP ADDRESS: 555.555.5.555 SERVER HOSTNAME: linuxbox CLIENT HOSTNAME: linuxbox PL/SQL procedure successfully completed.
The content of whoami.sql:
set serveroutput on begin dbms_output.put_line('USER: '||sys_context('userenv','session_user')); dbms_output.put_line('SESSION ID: '||sys_context('userenv','sid')); dbms_output.put_line('CURRENT_SCHEMA: '||sys_context('userenv','current_schema')); dbms_output.put_line('INSTANCE NAME: '||sys_context('userenv','instance_name')); dbms_output.put_line('CDB NAME: '||sys_context('userenv','cdb_name')); dbms_output.put_line('CONTAINER NAME: '||sys_context('userenv','con_name')); dbms_output.put_line('DATABASE ROLE: '||sys_context('userenv','database_role')); dbms_output.put_line('OS USER: '||sys_context('userenv','os_user')); dbms_output.put_line('CLIENT IP ADDRESS: '||sys_context('userenv','ip_address')); dbms_output.put_line('SERVER HOSTNAME: '||sys_context('userenv','server_host')); dbms_output.put_line('CLIENT HOSTNAME: '||sys_context('userenv','host')); end; /
Shortcut to get the name of the current container is:
SQL> show con_name CON_NAME ------------------------------ PDB1
You may find that useful in a multitenant environment with many Pluggable Databases within one Container Database
Tagged: 12c New Features, whoami
I just think this is a cool picture of an Oracle 12c instance and database from Oracle’s 12c Concepts manual (not my own work):
This is from the concepts manual found here: url
Just finished reading the book by Jonathan Lewis titled “Oracle Core: Essential Internals for DBAs and Developers“. I think I picked it up at the Collaborate 13 conference in Denver last April but haven’t had time (or taken the time) to read it.
Reading a book like Oracle Core can be a challenge because it is pretty dense with example scripts and outputs including dumps in hex. So, I decided to take the strategy of pushing myself to crash through the book without carefully following every example. I may only have absorbed about 10% of the material but if I didn’t jam through it I would have gotten 0%!
I picked up Oracle Core because I had read another book by the same author titled “Cost-Based Oracle Fundamentals” which has paid for itself 100 times over in terms of helping me tune queries. I highly recommend Cost-Based Oracle Fundamentals without reservation. But, like Oracle Core it can be a challenge to just sit down and read it and follow every SQL example and output. Probably it would be worth making a first pass focusing on just the English language text and skimming the examples, maybe delving into the examples of most interest.
In the case of Oracle Core I haven’t yet put it to practical use but I’m glad to have at least skimmed through it. Now I know what’s in it and can refer back to it when needed.
Next I hope to start reading up on Oracle 12c since I plan to get my certification this year. But, I wanted to finish Oracle Core before I moved on, even if I only read it at a high level.
It is amazing what Oracle Enterprise Manager 12c will report once it is configured for a product. Once such product is Oracle GoldenGate. I have stepped into a project where I’m running Oracle GoldenGate between many different environments for production purposes. Just trying to get a handle around what is going on has been a task. In talking with the customer, they were starting to implement Oracle Enterprise Manager 12c. Once OEM was setup, we added the Oracle GoldenGate plug-in and started to monitor the replication environments.
Monitoring the Oracle GoldenGate environments, I noticed a warning in the Incident Manager. The warning that was noticed was: “Status for Streams process OGG$_CGGMONX9AC55691 is DISABLED”. I got to thinking, what is this message about? Much more, how do I resolve this warning (I like OEM to be quite. I started to look around MOS for answers, to my surprise, not much is written about his message.
Oracle GoldenGate, classic capture, doesn’t report these types of messages within Oracle Enterprise Manager 12c. Classic Capture mostly reports the up and down status of Oracle GoldenGate processes. This message had to be coming from some integrated version of the extract (first clue was the word Streams). Keeping that Streams may be used in some way, the DBA_CAPTURE table should be able to shine a bit of light on this warning.
From a SQL*Plus prompt or an SQL IDE (prefer SQL Developer), the DBA_CAPTURE view can be queried.
From looking at the STATUS column, I verified that I’ve found the correct record. The PURPOSE column shows that this extract (capture) is being used for Streams. What!?, wait a minute, I’m using Oracle GoldenGate.
Yes, Oracle GoldenGate is being used. If there is information in the DBA_CAPTURE view it is because the Extract has been registered (integrated) with the database some how. The status is DISABLED, an indicator that this extract was registered for logretention:
GGSCI> stop extract cggmonx
GGSCI> dblogin userid ggate password ggate
GGSCI> register extract cggmonx logretention
GGSCI> start extract cggmonx
Now, that it is understood that the extract has been registered for log retention, what does this actually mean?
According to the Oracle GoldenGate 11g Reference Guide, an extract can be registered in one of two modes.
1. Database – Enables integrated capture for the Extract group. In this mode,
Extract integrates with the database logmining server to receive
change data in the form of logical change records (LCR). Extract
does not read the redo logs. Extract performs capture processing,
filtering, transformation, and other requirements
2. Logretention – Enables an Extract group, classic capture mode, to work with
Oracle Recovery Manager (RMAN) to retain the logs that Extract
needs for recovery
As indicated a few lines up, this extract has been registered with logretention. This means that the extract creates an underlying Streams capture process and prevents RMAN from removing any archivelogs that may be needed for replication of data. As part of creating the underlying Streams structure, Oracle creates a queue under the Oracle GoldenGate owner (The queue name can also be found in the DBA_CAPTURE view).
Now that the root problem of the DISABLE message in Oracle Enterprise Manager 12c has been identified, how can this message be resolved?
The simplest way is to unregister the extract from the database/logretention knowing that Oracle GoldenGate configuration is using Classic Capture. Keep in mind that when unregistering the extract, retention of archivelogs will not be enforced when RMAN backs them up and possibility removes them. Make sure you RMAN retention policies are what you expect them to be.
To unregister an extract that is using logretention, use the steps below:
GGSCI> stop extract cggmonx
GGSCI> dblogin userid ggate password ggate
GGSCI> unregister extract cggmonx logretention
GGSCI> start extract cggmonx
Filed under: Golden Gate, OEM
PLSQL has had the option for a long time
alter session set current_schema = SOME_SCHEMA_NAME;
This does not give you full schema owner capabilities ( well depends on what your login session capabilities have ) but can be very useful. For instance in some kind of script to validate that all the expected objects exist and are at the corrrect version you could use it like this.
set echo off
set feedback on
set heading off
set linesize 168
set serveroutput on size unlimited
set term on
alter session set current_schema = FIRST_SCHEMA_BEING_CHECKED;
validate_objects.bv_show_valid_messages := TRUE;
validate_objects.bv_stop_on_error := FALSE;
-- a bunch of calls against a validation package ... check that tables exists / views exists / foreign keys exists / indexes exist / packages procedures functions exists / data exists
-- at the end check that all objects are valid in the schema ...
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Just for fun I’ve pasted in a table listing the top 10 most viewed posts on this blog as links and including total number views since this blog began in March 2012. I based this on WordPress’s statistics so I’m not sure exactly how the blog software collects the numbers but it is fun to get some positive feedback. Hopefully it means people are getting something out of it. I’m certainly enjoying putting it together. Here are the links ordered by views as listed on the right:cell single block physical read 3,738 REGEXP_LIKE Example 2,822 Finding query with high temp space usage using ASH views 2,232 DBA_HIST_ACTIVE_SESS_HISTORY 2,097 CPU queuing and library cache: mutex X waits 1,801 DBMS_SPACE.SPACE_USAGE 1,748 Resource Manager wait events 1,566 Fast way to copy data into a table 1,166 Delphix First Month 1,074 use_nl and use_hash hints for inner tables of joins 1,047
Anyway, I thought I would list the top ten posts on this blog if you want to read the ones that have the most views and possibly are the most useful.
Our monitoring software found a long running job on one of our client’s databases. The job was an Oracle’s auto task running statistics gathering for more than 3 hours. I was curious to know why it took so long and used a query to ASH to find out the most common SQL during the job run based on the module name. Results were surprising to me: top SQL was coming with SQL Tuning Advisor comment.
Here is the SQL I used:
SQL> select s.sql_id, t.sql_text, s.cnt 2 from 3 (select * 4 from 5 ( 6 select sql_id, count(*) cnt 7 from v$active_session_history 8 where action like 'ORA$AT_OS_OPT_SY%' 9 group by sql_id 10 order by count(*) desc 11 ) 12 where rownum <= 5 13 ) s, 14 dba_hist_sqltext t 15 where s.sql_id = t.sql_id; SQL_ID SQL_TEXT CNT ------------- -------------------------------------------------------------------------------- ---------- 020t65s3ah2pq select substrb(dump(val,16,0,32),1,120) ep, cnt from (select /*+ no_expand_table 781 byug0cc5vn416 /* SQL Analyze(1) */ select /*+ full(t) no_parallel(t) no_parallel_index(t) 43 bkvvr4azs1n6z /* SQL Analyze(1) */ select /*+ full(t) no_parallel(t) no_parallel_index(t) 21 46sy4dfg3xbfn /* SQL Analyze(1) */ select /*+ full(t) no_parallel(t) no_parallel_index(t) 1559
So most queries are coming with “SQL Analyze” comment right in the beginning of SQL which is running from DBMS_STATS call, which is confusing. After some bug search I have found a MOS Doc ID 1480132.1 which includes a PL/SQL stack trace from a DBMS_STATS procedure call, and it is going up to DBMS_SQLTUNE_INTERNAL, which means DBMS_STATS has a call to the SQL Tuning package; very odd:
SQL> select * from dba_dependencies where name = 'DBMS_STATS_INTERNAL' and referenced_name = 'DBMS_SQLTUNE_INTERNAL'; OWNER NAME TYPE REFERENCED_OWNER REFERENCED_NAME ------------------------------ ------------------------------ ------------------ ------------------------------ ---------------------------------- REFERENCED_TYPE REFERENCED_LINK_NAME DEPE ------------------ ------------------------------------------------------------------------------------------------------------------------------- SYS DBMS_STATS_INTERNAL PACKAGE BODY SYS DBMS_SQLTUNE_INTERNAL PACKAGE HARD
Turns out, this call has nothing to do with the SQL Tuning. It is just a call to a procedure in this package, which happen to look like an SQL from SQL Tuning Advisor. I have traced a GATHER_TABLE_STATS call in a test database first with SQL trace and then with DBMS_HPROF and here is how the call tree looks like:
SELECT RPAD(' ', (level-1)*2, ' ') || fi.owner || '.' || fi.module AS name, fi.function, pci.subtree_elapsed_time, pci.function_elapsed_time, pci.calls FROM dbmshp_parent_child_info pci JOIN dbmshp_function_info fi ON pci.runid = fi.runid AND pci.childsymid = fi.symbolid WHERE pci.runid = 1 CONNECT BY PRIOR childsymid = parentsymid START WITH pci.parentsymid = 27; NAME FUNCTION SUBTREE_ELAPSED_TIME FUNCTION_ELAPSED_TIME CALLS ---------------------------------------- ------------------------------ -------------------- --------------------- -------------------- ... SYS.DBMS_STATS_INTERNAL GATHER_SQL_STATS 21131962 13023 1 SYS.DBMS_ADVISOR __pkg_init 88 88 1 SYS.DBMS_SQLTUNE_INTERNAL GATHER_SQL_STATS 21118776 9440 1 SYS.DBMS_SQLTUNE_INTERNAL I_PROCESS_SQL 21107094 21104225 1 SYS.DBMS_LOB GETLENGTH 37 37 1 SYS.DBMS_LOB INSTR 42 42 1 SYS.DBMS_LOB __pkg_init 15 15 1 SYS.DBMS_SQLTUNE_INTERNAL I_VALIDATE_PROCESS_ACTION 74 39 1 SYS.DBMS_UTILITY COMMA_TO_TABLE 35 35 1 SYS.DBMS_SQLTUNE_UTIL0 SQLTEXT_TO_SIGNATURE 532 532 1 SYS.DBMS_SQLTUNE_UTIL0 SQLTEXT_TO_SQLID 351 351 1 SYS.XMLTYPE XMLTYPE 1818 1818 1 SYS.DBMS_SQLTUNE_UTIL0 SQLTEXT_TO_SQLID 528 528 1 SYS.DBMS_UTILITY COMMA_TO_TABLE 88 88 1 SYS.DBMS_UTILITY __pkg_init 10 10 1 SYS.SQLSET_ROW SQLSET_ROW 33 33 1 SYS.XMLTYPE XMLTYPE 1583 1583 1 SYS.DBMS_STATS_INTERNAL DUMP_PQ_SESSTAT 73 73 1 SYS.DBMS_STATS_INTERNAL DUMP_QUERY 2 2 1 ...
So there is a procedure DBMS_SQLTUNE_INTERNAL.GATHER_SQL_STATS which is being called by DBMS_STATS_INTERNAL, and this procedure actually runs a SQL like this:
/* SQL Analyze(0) */ select /*+ full(t) no_parallel(t) no_parallel_index(t) dbms_stats cursor_sharing_exact use_weak_name_resl dynamic_sampling(0) no_monitoring no_substrb_pad */to_char(count("ID")),to_char(substrb(dump(min("ID"),16,0,32),1,120)),to_char(substrb(dump(max("ID"),16,0,32),1,120)),to_char(count("X")),to_char(substrb(dump(min("X"),16,0,32),1,120)),to_char(substrb(dump(max("X"),16,0,32),1,120)),to_char(count("Y")),to_char(substrb(dump(min("Y"),16,0,32),1,120)),to_char(substrb(dump(max("Y"),16,0,32),1,120)),to_char(count("PAD")),to_char(substrb(dump(min("PAD"),16,0,32),1,120)),to_char(substrb(dump(max("PAD"),16,0,32),1,120)) from "TIM"."T1" t /* NDV,NIL,NIL,NDV,NIL,NIL,NDV,NIL,NIL,NDV,NIL,NIL*/
Which is basically approximate NDV calculation. So, nothing to be afraid of, it’s just the way the code is organized: DBMS_STATS uses API of SQL Tuning framework when you are using DBMS_STATS.AUTO_SAMPLE_SIZE as the ESTIMATE_PERCENT (which is the default & recommended value in 11g+).