Initialization parameters

• v$streams_capture
   

• v$streams_apply_coordinator
   

• v$streams_apply_reader
   

• v$streams_apply_server

The collection of timing details yields information that is useful to the DBA for monitoring and analyzing the performance load issues.

The next section introduces information on the creation of the Streams pool in the SGA and its true nature.

Streams Pool in the SGA

Unlike a persistent AQ queue, which stages all events in a queue table on disk, a Streams queue has a queue buffer that is used to stage captured events in shared memory.  A queue buffer is memory associated with a SYS.AnyData queue that contains only the captured events. The queue buffering mechanism enables the database to optimize captured events by buffering them in the SGA instead of always storing them in a queue table on disk.

By default in earlier releases of the Oracle database, the memory used by Streams was allocated from the Shared Pool.  The size was limited to 10% of the Shared pool which was controlled by the parameter shared_pool_size. In many instances, the buffer would overflow due to speedier capture activity.