Streams Pool Size Set by Default--关于流池

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Streams Pool Size Set by Default

If both the

STREAMS_POOL_SIZE

and the

SGA_TARGET

initialization parameters are set to

0

(zero), then, by default, the first use of Streamsin a database transfers an amount of memory equal
to 10% of theshared pool from the buffer cache to the Streamspool. The buffer cache is set by the

DB_CACHE_SIZE

initialization parameter, and the sharedpool size is set by the

SHARED_POOL_SIZE

initialization parameter.

For example, consider the following configuration in a databasebefore Streams is used for the first time:

DB_CACHE_SIZE

is set to 100MB.

SHARED_POOL_SIZE

is set to 80MB.

STREAMS_POOL_SIZE

is set tozero.

SGA_TARGET

is set to zero.

Given this configuration, the amount of memory allocated afterStreams is used for the first time is the following:

The buffer cache has 92 MB.

The shared pool has 80 MB.

The Streams pool has 8 MB.

The first use of Streams in a database is the first attempt toallocate memory from the Streams pool. Memory is allocated from theStreams pool in the following ways:

A message is enqueued into a buffered queue. The message can bean LCR captured by a capture process, or it can be a user-enqueuedLCR or message.

A capture process is started.

An apply process is started.