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Oracle Tips by Burleson Consulting
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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$process view can be used to display the existing values for
the new Oracle parameters.
column name format 999,999,999,999
select
name,
value
from
v$parameter
where
name in
(
'sga_max_size',
'shared_pool_size',
'db_cache_size',
'large_pool_size',
‘pga_aggregate_target’
)
;
NAME VALUE
-------------------- -------------
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.
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