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Oracle Tips by Burleson |
Oracle10g Database 10g Automatic Shared Memory Management (ASMM)
Oracle Database 10g now has Automatic Memory Management (ASMM) in the
form of the one-size-fits-all parameter called sga_target, which
replaces many individual parameters and automates the allocation of
RAM between the data buffers, shared pool, and log buffers.
The tuning of these SGA memory regions used to be complex and time
consuming, until ASMM automated the tuning. Using predictive models
derived from v$db_cache_advice and v$shared_pool_advice, Oracle
automatically monitors changing demands on the SGA regions and
re-allocates RAM memory based on the existing workload.
Let’s take a close look at the ASMM simplification. When using ASMM, we
only have three instance parameters:
sga_max_size -- This parameter sets the hard limit up to which
sga_target can dynamically adjust sizes. Usually, sga_max_size and
sga_target will be the same value, but there may be times when you
want to have the capability to adjust for peak loads. By setting this
parameter higher than sga_target, you allow dynamic adjustment of the
sga_target parameter.
sga_target -- This parameter is new in Oracle Database 10g and
reflects the total size of memory footprint a SGA can consume. It
includes in its boundaries the fixed SGA and other internal
allocations, the (redo) log buffers, the shared pool, Java pool,
streams pool, buffer cache, keep/recycle caches, and if they are
specified, the non-standard block size caches.
pga_aggregate_target -- This parameter defines the RAM area
reserved for system-wide sorting and hash joins.
Get the complete Oracle10g story:
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http://www.rampant-books.com/book_2003_2_oracle10g.htm
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