You need to check the time interval value, not the absolute value in v$sysstat, this value can be reseted due to overflow. On 9/14/05, Chirag DBA <chiragdba@xxxxxxxxx> wrote: > > Hi Team, > My OEM shows buffer cache hit ratio as 28% and library cache as 99%. > Another query shows different results for buffer cache. > > SQL> SELECT NAME,100-PHYSICAL_READS/(DB_BLOCK_GETS + CONSISTENT_GETS) FROM > V$BUFFER_POOL_STATISTICS; > > NAME 100-PHYSICAL_READS/(DB_BLOCK_GETS+CONSISTENT_GETS) > -------------------- -------------------------------------------------- > DEFAULT 99.9072457 > > SQL> show sga > > Total System Global Area 252273320 bytes > Fixed Size 434856 bytes > Variable Size 150994944 bytes > Database Buffers 100663296 bytes > Redo Buffers 180224 bytes > > And my db_block_buffers show value as 0. > > but it should be the value of database buffers / db_block_size . > > SQL> show parameter db_block > > NAME TYPE VALUE > ------------------------------------ ----------- ---------------------- > db_block_buffers integer 0 > db_block_checking boolean FALSE > db_block_checksum boolean TRUE > db_block_size integer 8192 > > Is really my buffer cache hits very low? > > Regards - Chirag > -- Welcome, Fangxin.Lou from China Home: http://www.anysql.net/en/ Mydul: http://www.anysql.net/en/mydul.html