_optimizer_use_feedback

There is a bug in 11.2.0.2 and 11.2.0.3 that causes worse plan. need to add hint /*+OPT_PARAM('_optimizer_use_feedback','false') */ to resolve the issue.

 symptom:
first run --fast
second and onward runs --very slow
do 10046, you will see a lot of physical reads query on v$sql, you will see the plan_hash_values are different.

How to fix ORA-01103 during DB clone

Option 1: CREATE CONTROLFILE REUSE SET DATABASE dbname LOGFILE GROUP 1 ('FILENAME','FILENAME2') SIZE 50K, GROUP 2 ('FILENAME','FILENAME2') SIZE 50K RESETLOGS DATAFILE 'FILENAME' SIZE 2M Option 2: use backup controlfile to trace Option 3: Use NID to reset DBname