Friday Nov 07, 2014

Sleeping Beauties - Upgrade to 11.2.0.4 can be slow

A customer from the US did contact me past week via LinkedIn and raised a question:

"Is it expected that my patch set upgrade from Oracle 11.2.0.3 to Oracle 11.2.0.4 takes over 3 hours?"

Of course, no - this is not expected

This is the upgrade stats gathered post upgrade with utlu112s.sql:

SQL> @?/rdbms/admin/utlu112s.sql ; .
Oracle Database 11.2 Post-Upgrade Status Tool 10-31-2014 10:05:29
Component Current Version Elapsed Time
Name Status Number HH:MM:SS
Oracle Server  
. VALID 11.2.0.4.0 02:46:19
JServer JAVA Virtual Machine
. VALID 11.2.0.4.0 00:08:34
[..]
Final Actions
. 00:00:00
Total Upgrade Time: 03:06:47

No, this is not really expected. So we tried to nail down the root cause finding out these statements in the upgrade script c1102000.sql are causing the trouble:

194 -- wri$_optstat_histhead_history2.
195 execute immediate
196 q'#create unique index i_wri$_optstat_hh_obj_icol_st on
197 wri$_optstat_histhead_history (obj#, intcol#, savtime, colname)
198 tablespace sysaux #';
199
200 execute immediate
201 q'#create index i_wri$_optstat_hh_st on
202 wri$_optstat_histhead_history (savtime)
203 tablespace sysaux #';
204 end;
205 /

It's index rebuilds on histogram tables. And the customer has a large amount of stats data in his database as the default stats retention is 31 days.

Obviously the index rebuild is not done very efficiently (not done in parallel, no nologging clause). Those things can happen and sometimes this may not cause any issues. But in this case it lead to over 2 hours for just those index rebuilds.  

Luckily my colleague Cindy is an excellent resource for such things - after asking our team I've got the reply that this is tagged with a bug number and code fix already got checked in (under review right now):

bug19855835:
Upgrade from 11.2.0.2 to 11.2.0.4 is slow 

-Mike

PS: Credits go to Tan for bringing this to my attention - and sorry for the inconvenience! 

Thursday Apr 17, 2014

Avoid Poor Performance and Wrong Results in 11.2.0.4

One of the best notes in MOS got refreshed last night for Oracle Database 11.2.0.4. It has not only information about performance bugs but also about the worst and meanest category of issues, wrong query result bugs. Those are the ones I call the "sleeping beauties" as you as a DBA usually won't recognize them. It is recognized at the application level when the result of a report is incorrect or instead of 4 rows just 3 rows get delivered in the output. Therefore you should be highly aware of those and add this note to your bookmarks.

MOS Note 1645862.1Things to Consider Before Upgrading to 11.2.0.4 to Avoid Poor Performance or Wrong Results

And in case you don't want to move to Oracle 11.2.0.4 but searching for information and known issues in Oracle 11.2.0.3 or Oracle 11.2.0.2 then please find the corresponding documents:

  • MOS Note: 1320966.1 Things to Consider Before Upgrading to 11.2.0.2.x to Avoid Poor Performance or Wrong Results
  • MOS Note: 1392633.1 Things to Consider Before Upgrading to 11.2.0.3 to Avoid Poor Performance or Wrong Results
-Mike
About

Mike Dietrich - Oracle Mike Dietrich
Master Product Manager - Database Upgrade & Migrations - Oracle Corp

Based near Munich/Germany and spending plenty of time in airplanes to run either upgrade workshops or work onsite or remotely with reference customers. Acting as interlink between customers/partners and the Upgrade Development.

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