Recently, after an upgrade from 11.2 to 12.1, we ran across some performance problems. Eventually we found that the SQL Tuning Advisor was missing. The cause was BUG 20540751.
Oracle offers both a patch and a work around. If you find this as part of your upgrade testing, before your production upgrade, the patch number is 20540751 and it can be applied as part of your upgrade outage window. If you are seeing performance problems after an upgrade, check for this bug by running the SQL below and apply the work around.
There is nothing in the upgrade log to let you know you have hit this bug, and it’s not clear what causes it to appear. It wouldn’t hurt to add a step to your post upgrade checklist to make sure the SQL Tuning Advisor job still exists.
Bug 20540751 – AUTO TASK SQL TUNING ADVISOR ENABLED BUT PROGRAM NOT RUNNING AFTER 12C UPGRADE. This affects versions 126.96.36.199 and 188.8.131.52.
If you have recently upgraded and are experiencing performance problems check to see if your SQL Tuning Advisor job is missing by running this:
SQL > select program_name, program_action from dba_scheduler_programs where program_name = 'AUTO_SQL_TUNING_PROG'; no rows selected
If you see “no rows selected” then you have hit this bug.
The workaround from Oracle is to run:
to create the scheduler program that was dropped.
See Oracle Support Note: Doc ID 2171154.1 for more info, go to: https://support.oracle.com/
For additional resources please see our white paper: Upgrading to Oracle 12c.
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The “ORA-12154: TNS:could not resolve the connect identifier specified” Oracle error is a commonly seen message for database administrators.