Well, the initial sizing is the matter of opinion. I usually start with 256M and then increase until waits on free buffers go away or until the end users are satisfied with the performance, whichever happens first. It's the end luser that is driving the tuning process, not the DBA. I also subscribe to the binary religion: I somehow believe (from the days of mVaxII) that binary numbers are easier for the CPU to operate on and that using binary numbers will help me secure the afterlife and not re-incarnate as a MS-Windows workstation. -- Mladen Gogala Ext. 121 -----Original Message----- From: Michael McMullen [mailto:ganstadba@xxxxxxxxxxx] Sent: Wednesday, September 14, 2005 12:20 PM To: oracle-l@xxxxxxxxxxxxx Subject: how do you decide your db_cache_size In reference to Buffer Cache hit very low I should have said keep the SGA below 2GB but I'm standing by enlarging the buffer cache. I never said it would help the BCHR. I'm a firm believer in method R and I don't live in Kittrell NC but to exaggerate to make a point what if your buffer cache is 1Mb? Do you still say figure out your bad sql? No, you increase it, then work on the bad sql. Personally, I think an 250Mb cache size for a 40Gb database doing large batch jobs is too small and really the db_cache_size would be lower as I think that was referring to total SGA.