MEMORY_TARGET
Even though MEMORY_TARGET is not a ???basic??? parameter according to the Oracle documentation,
it can greatly simplify instance memory management. This parameter specifies the Oracle systemwide
usable memory; Oracle in turn reallocates memory between, for example, the SGA and PGA
to optimize performances.
DB_CACHE_SIZE and DB_nK_CACHE_SIZE
The parameter DB_CACHE_SIZE specifies the size of the area in the SGA to hold blocks of the
default size, including those from the SYSTEM, TEMP, and SYSAUX tablespaces. Up to four other
caches can be defined if there are tablespaces with block sizes other than the SYSTEM and
SYSAUX tablespaces. The value of n can be 2, 4, 8, 16, or 32; if the value of n is the same as the
default block size, the corresponding DB_nK_CACHE_SIZE parameter is illegal. Although this
parameter is not one of the basic initialization parameters, it becomes very basic when you
transport a tablespace from another database with a block size other than DB_BLOCK_SIZE!
There are distinct advantages to a database containing multiple block sizes. The tablespace
handling OLTP applications can have a smaller block size, and the tablespace with the data
warehouse table can have a larger block size. However, be careful when allocating memory for
each of these cache sizes so as not to allocate too much memory for one at the expense of
another. As of Oracle9i, Oracle??™s Buffer Cache Advisory feature monitors the cache usage for each
cache size in the view V$DB_CACHE_ADVICE to assist the DBA in sizing these memory areas.
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