Blog dedicated to Oracle Applications (E-Business Suite) Technology; covers Apps Architecture, Administration and third party bolt-ons to Apps

Monday, June 29, 2009

RMAN works best with RBO

Eventhough Oracle forced everyone to move to Cost Based Optimizer (CBO), their own tools continue to use RBO. RMAN is a classic example. Refer to Metalink Note 375386.1 which describes performance problems selecting from V$RMAN_STATUS. The cause is given as bug 5247609 and workaround provided is:

Add the following to your rman script:

sql "alter session set optimizer_mode=RULE";

A few customers have found that using RULE does not workaround this but gathering fixed statistics does:

SQL> exec dbms_stats.gather_fixed_objects_stats()

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