For example, if your
standard database block size is 4KB, you can also specify a cache for
the 8KB block size tablespaces via the DB_8K_CACHE_SIZE parameter.
256 Oracle Database 11g DBA Handbook
For example, you may specify the following:
SGA_MAX_SIZE=1024M
SHARED_POOL_SIZE=220M
DB_BLOCK_SIZE=8192
DB_CACHE_SIZE=320M
DB_4K_BLOCK_SIZE=4M
With these parameters, 4MB will be available for data queried from objects in tablespaces
with 4KB block sizes. Objects using the standard 8KB block size will use the 160MB cache.
While the database is open, you can change the SHARED_POOL_SIZE and DB_CACHE_SIZE
parameter values via the alter system command.
SGA_TARGET is a dynamic parameter and can be changed through Database Control or with
the alter system command.
SGA_TARGET can be increased up to the value of SGA_MAX_SIZE. It can be reduced until any
one of the auto-tuned components reaches its minimum size??”either a user-specified minimum or
an internally determined minimum. Both of these parameters can be used to tune the SGA.
Using the Cost-Based Optimizer
With each release of its software, Oracle has added new features to its optimizer and has enhanced
existing features. Effective use of the cost-based optimizer requires that the tables and indexes
in your application be analyzed regularly. The frequency with which you analyze the objects
depends on the rate of change within the objects. For batch transaction applications, you should
reanalyze the objects after each large set of batch transactions.
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