RE: High mbrc in aux_stats$

An important point to note in 10gR2 is that you have two new db_file_multiblock_read_count parameters:

On my system:

_db_file_exec_read_count 95
_db_file_optimizer_read_count 8

leading to:

    db_file_multiblock_read_count                 95

I haven't tested this yet (still doing lots with an explicit db_file_multiblock_count, which forces both the others to match the set value).

Working hypothesis: Oracle has finally separated the two functions of the db_file_Mulitblock_read_count: one as the value to be used by the optimizer (in the absence of an observed MBRC) for the arithmtic, and one to be attempted at run time when executing the query). The MBRC you finally gather will be probably be based on the actual run-time activity, and will then over-ride the _db_file_optimizer_read_count next time around the optimization cycle.

Regards

Jonathan Lewis

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