At some later time, those changes will be written to
the datafile in which the block resides. This avoids making users wait while Oracle
writes their changed blocks to disk.
This notion of waiting to perform I/O until absolutely necessary is common throughout
Oracle. Disks are the slowest component of a computer system, so the less I/O
performed, the faster the system runs. By deferring noncritical I/O operations instead
of performing them immediately, an Oracle database can deliver better performance.
Since Oracle8, the database buffer cache can be configured with buffer pools of the
following types:
DEFAULT
The standard Oracle database buffer cache. All objects use this cache unless otherwise
indicated.
KEEP
For frequently used objects you wish to cache.
RECYCLE
For objects you??™re less likely to access again.
Instance Memory and Processes | 51
Both the KEEP and RECYCLE buffer pools remove their objects from consideration
by the LRU algorithm.
Youcan mark a table or index for caching in a specific buffer pool. This helps to
keep more desirable objects in the cache and avoids the ???churn??? of all objects fighting
for space in one central cache.
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