I am experiencing the same symptoms as noted in this question which was closed and does not have a satisfactory answer.

Original Question We've recently upgraded from Oracle 10gR2 (10.2.0.4 ) to 11gR2 (11.2.0.3) and we are noticing a significant hit in performance although execution plans are the same for the offended queries before and after the upgrade. Allocation of more memory did improve the performance but just slightly. We also tried to set optimizer mode to 10204 at session level but queries produced no better results. The only difference we've noticed is when enabling autotrace the physical reads on 10gR2 were 0 whereas on 11gR2 it was of the magnitude of tens of thousands.

Including stats demonstrating the physical reads discrepancies:

10gR2 Stats

Statistics
--------------------------------------------------------
          0  recursive calls
          0  db block gets
      21189  consistent gets
          0  physical reads
          0  redo size
       1014  bytes sent via SQL*Net to client
        492  bytes received via SQL*Net from client
          2  SQL*Net roundtrips to/from client
          0  sorts (memory)
          0  sorts (disk)
          1  rows processed



11gR2
~~~~~~
Statistics
------------------------------------------------------
          0  recursive calls
          0  db block gets
      11243  consistent gets
      11232  physical reads
          0  redo size
       1049  bytes sent via SQL*Net to client
        524  bytes received via SQL*Net from client
          2  SQL*Net roundtrips to/from client
          0  sorts (memory)
          0  sorts (disk)
          1  rows processed
Any ideas/suggestions/right-directions would be greatly appreciated.

I am experiencing the same symptoms as noted in this question which was closed and does not have a satisfactory answer.

Original Question We've recently upgraded from Oracle 10gR2 (10.2.0.4 ) to 11gR2 (11.2.0.3) and we are noticing a significant hit in performance although execution plans are the same for the offended queries before and after the upgrade. Allocation of more memory did improve the performance but just slightly. We also tried to set optimizer mode to 10204 at session level but queries produced no better results. The only difference we've noticed is when enabling autotrace the physical reads on 10gR2 were 0 whereas on 11gR2 it was of the magnitude of tens of thousands.

Including stats demonstrating the physical reads discrepancies:

10gR2 Stats

Statistics
--------------------------------------------------------
          0  recursive calls
          0  db block gets
      21189  consistent gets
          0  physical reads
          0  redo size
       1014  bytes sent via SQL*Net to client
        492  bytes received via SQL*Net from client
          2  SQL*Net roundtrips to/from client
          0  sorts (memory)
          0  sorts (disk)
          1  rows processed



11gR2
~~~~~~
Statistics
------------------------------------------------------
          0  recursive calls
          0  db block gets
      11243  consistent gets
      11232  physical reads
          0  redo size
       1049  bytes sent via SQL*Net to client
        524  bytes received via SQL*Net from client
          2  SQL*Net roundtrips to/from client
          0  sorts (memory)
          0  sorts (disk)
          1  rows processed
Any ideas/suggestions/right-directions would be greatly appreciated.

A question was earlier posted, but then closed by Jack Douglas because he stated it was not a real question. I am having the same issue as the person who originally posted the question and I don't know how it could be stated any more clearly. So to say it's not a real question makes no sense. Below is the question that was originally asked. It is a serious problem for some people who upgraded to 11gR2. If an expert cannot answer it, please don't close it. Please leave it for someone who can provide some help on the issue.

I am experiencing the same symptoms as noted in this question which was closed and does not have a satisfactory answer.