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Oracle and UNIX granules

Starting with Oracle, Oracle expands the term granule to include a reserved region of RAM memory for SGA growth. A memory granule should not be confused with Oracle parallel query block range partition granules. Block range partition granules are used by OPQ to determine the block ranges for parallel query slaves, while a RAM memory granule is a unit of contiguous virtual memory allocation. If the current amount of SGA memory is less than the value of the sga_max_size init.ora parameter, then Oracle is free to allocate more granules until the SGA size reaches the sga_max_size limit.

In Oracle, the DBA “reserves” granules for use by the dynamic SGA feature. When the DBA issues an alter system command to increase the size of a RAM memory region of the SGA, Oracle passes the command to a background process that allocates the RAM memory from the reserved space, adding the memory to the desired SGA component.

Note: At this time, Oracle does not support dynamic modification of the large_pool_size parameter and the sga_max_size parameter.

The v$process view can be used to display the existing values for the new Oracle parameters.

column name format 999,999,999,999

name in

-------------------- -------------
shared_pool_size 40,362,826
sga_max_size 5,392,635,193
large_pool_size 1,048,576
db_cache_size 4,194,304
pga_aggregate_target 2,403,628,363

This query gives us the current values of the dynamic memory parameters and allows the DBA to compare existing demands with current instance settings.

The above is an excerpt from the "Oracle UNIX Administration Handbook" by Oracle press, authored by Donald K. Burleson.


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