Brandon > Am I missing something, or isn't it best to just leave this parameter > unset (default) in 10.2, in which case Oracle will automatically adjust > it to the max io size of your OS? Mhmm... I don't like that for the simplest reason that the maximum is not the best value for performance! As the OP noticed... > Along with computing system stats on a typical workload so you have an > accurate mbrc, you should get the best of both worlds - accurate costing > and optimized sequential scans, right? In some situations, as I just wrote, no. > I have it unset on my 10.2 AIX 5.3 system and it has defaulted to 128 > with an 8k block size (1MB). Notice that there are some limits... According to my tests the value of db_file_multiblock_read_count is calculated with the following formula: min( DbCacheSize/(Sessions*DbBlockSize) , 1048576/DbBlockSize ) Regards, Chris -- //www.freelists.org/webpage/oracle-l