|Oracle9i Database Reference
Release 1 (9.0.1)
Part Number A90190-02
Initialization Parameters, 32 of 220
Derived: 48 MB /
|Range of values||
50 to an operating system-specific maximum
|Oracle9i Real Application Clusters||
Multiple instances can have different values, and you can change the values as needed.
This parameter is deprecated in favor of the
DB_BLOCK_BUFFERS specifies the number of database buffers in the buffer cache. It is one of several parameters that contribute to the total memory requirements of the SGA of an instance.
This parameter, together with
DB_BLOCK_SIZE, determines the total size of the buffer cache. Effective use of the buffer cache can greatly reduce the I/O load on the database.
DB_BLOCK_SIZE can be specified only when the database is first created, so you use
DB_BLOCK_BUFFERS to control the size of the buffer cache.
The buffers for the
" buffer pool and the "recycle" buffer pool come out of the buffer cache. In addition, each LRU list in the buffer cache must have at least 50 buffers. Therefore, if you specify
BUFFER_POOL_RECYCLE, be sure the value of
DB_BLOCK_BUFFERS conforms to the following formula:
DB_BLOCK_BUFFERS > #_buffers_in_"keep"_buffer_pool + #_BUFFERS_IN_"recycle"_buffer_pool + 50*(DB_BLOCK_LRU_LATCHES - #_lru_latches_in_"keep"_buffer_pool - #_lru_latches_in_"recycle"_buffer_pool)
If you did not specify any LRU latches in
BUFFER_POOL_RECYCLE, then the values default to 1.
This parameter affects the probability of data block pinging when Oracle9i Real Application Clusters are enabled: the more buffers, the greater the chance of pinging.