EBS Database performance degraded after upgrade to 19c

[soumya]

Hi Erman,

Hope are you doing well.

Recently, We have upgraded database from 11.2.0.4 to 19c in one of our test EBS R12.1.3 instance in OEL 7.9.  The upgrade went well, however we are observing many issues related to slow performance. We have done already basic stuffs like gather statistics for  schema, gather statistics for fixed objects , dictionary objects etc, compilation of invalid objects. But now we are not sure what else to look for or what are the best practices for post upgrade. Any help in this regard would be really appreciated.

Thanks again for all the work you have been doing for the community. Best Wishes.

Regards,
Soumya

[ErmanArslansOracleBlog]

If you have already optimized the instance parameters, then you have to check the failing SQLs one by one.. Execution plans may be the problem.. SQL PLAN management may needs to be implemented.. SQL Profile and Plan setting may need to be done for them.. Optimizer_features_enable may be the problem (for the custom code).. If those SQLs are being executed from standard EBS programs then there may be some patches you need to apply..
This is a big subject.. Read my related blog post to get some insight.

https://ermanarslan.blogspot.com/2020/12/ebs-122-rdbms-optimizerfeaturesenable.html

https://ermanarslan.blogspot.com/2021/01/ebs-122-19c-db-environments-suggestions.html