||Oracle Tips by Burleson
Using Oracle STATSPACK for the Data
Buffer Hit Ratio
STATSPACK uses the
stats$buffer_pool_statistics table for monitoring buffer pool
statistics. This table contains the following useful columns:
name - This column shows the name of the data buffer
(KEEP, RECYCLE, or DEFAULT).
free_buffer_wait - This is a count of the number of
waits on free buffers.
buffer_busy_wait - This is the number of times a
requested block was in the data buffer but unavailable because of a
db_block_gets - This is the number of database block
gets, which are either logical or physical.
consistent_gets - This is the number of logical reads.
physical_reads - This is the number of disk block
fetch requests issued by Oracle. (Remember, this is not always a “real”
read because of disk array caching.)
physical_writes - This is the number of physical disk
write requests from Oracle. If you have a disk array, the actual writes are
These STATSPACK columns provide
information that can be used to measure several important metrics,
including the most important, the data buffer hit ratio.
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