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Upgrade to Oracle 11g results in queries running much slower in compared to Oracle 10g

edited Jan 28, 2014 8:56AM in SQL Performance (MOSC) 22 commentsAnswered

I am a newbie with Oracle so I apologize if this issue is obvious.  I've been tasked with trying to track down why our application runs at a snails pace on faster hardware and upgraded from Oracle 10g to 11g  We've been reading through numerous forums on migrating execution plans and statistics and trying the suggestions.  Unfortunately we have not had any success even getting the plans out of our Oracle 10g system.

Our current system is running on Oracle 10g (10.1.0.5.0) and we have been planning the migration of the current system to new hardware which has been setup with Oracle 11g (11.2.0.4.0).  Unfortunately we are having some trouble with our Oracle 11g test environment in regards to VERY long running SQL queries.  We have discovered that the Query Optimizer is producing some very inefficient execution plans which make use of FULL SCANS rather than INDEX's for table access.  We also noticed that the 10g plan has the word PARTITION next to the UNION-ALL operation.  This same query in our current production

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