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Donald K. Burleson
Oracle Tips |
SGA Regions
Now, let's take a quick look at the important regions within the SGA. The
most important areas of RAM within the SGA include:
Data Buffer Caches These RAM areas define RAM space for incoming data
blocks and are governed by the following parameters. The sum of all of
these parameter values determines the total space reserved for Oracle data
blocks.
db_cache_size
db_keep_cache_size)
db_recycle_cache_size
db_2k_cache_size
db_4k_cache_size
db_8k_cache_size
db_16k_cache_size
db_32k_cache_size
Log Buffer This is the RAM space for writing redo log files. The
log_buffer parameter should never exceed 5 megabytes, and this RAM space is
used solely to hold the redo images until the LGWR background process
writes the redo log entries into the redo log filesystem.
Shared Pool - This RAM area is used to process SQL statements (inside a
shared pool area called the library cache) and hold control structures for
the instance. It is governed by the shared_pool_size parameter.
To re-allocate RAM within Oracle, we use alter system commands to change
important Oracle parameters that govern the size of the memory regions
within the SGA. Lets take a close look at these parameters and see how
they are used.
The above
text is an excerpt from "Creating
a Self Tuning Oracle Database", by Rampant TechPress. It is only
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