RE: Oracle SGA and HPUX Buffer Cache

UNIX in general uses buffer to maximize I/O efficiency regardless what is writting. Oracle tries to maximize how it offloads data to UNIX. This is fair and competitive - this is like a free market economy where everyone tries to get the best deal. Oracle sends it's buffers when it feels it is efficient to do so( based on DBA configuration). Oracle for buffer writes will go through the UNIX buffer caches except for writes to the redo logs. The LGWR for best chance at consistency needs to bypass the UNIX buffers so it is assurred that what it wants to write is actually written on return of ORACLES write API call. If wrote to the UNIX buffers it wouldn't know when it its data was written. This is vital in case of recovery.

Your other question about balancing UNIX memory and ORACLE buffer cache, log buffer and shared pool has not simple solution. I may have time to discuss this in future but for now may time is up. See Oracle Performance tuning by O'Reilly and Associates. Received on Sun Jun 23 1996 - 00:00:00 CEST