Oracle9i enabled dynamic resizing of these pools
based on a minimum memory allocation called a granule. Oracle Database 10g and
later releases can automatically manage shared memory. Oracle Database 11g adds
automatic memory management of the SGA and PGA.
Exhausting a database server??™s supply of memory will cause poor performance. If you
are running an older release of Oracle, you should gauge the size of the various memory
areas Oracle uses or add more memory to the machine to prevent a memory deficit
from occurring. What constitutes the right size for the various areas is a function
of your application behavior, the data it uses, and your performance requirements.
How Oracle Uses the System Global Area
Oracle uses the SGA for the following operations:
??? Caching of database blocks containing table and index data in the database
buffer cache
??? Caching of parsed and optimized SQL statements, stored procedures, and data
dictionary information in the shared pool
??? Buffering of redo log entries in the redo log buffer before they??™re written to disk
In versions prior to Oracle 9i, the amount of memory allocated to each of these areas
within the SGA was determined at instance startup using initialization parameters
and could not be altered without restarting the instance.
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