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Oracle Tips by Burleson |
Oracle Streams
Chapter 4 -
Capture
and Propagate Configuration
Creating Queues and Queue tables
SELECT q.OWNER, q.NAME, t.QUEUE_TABLE,
q.USER_COMMENT
FROM DBA_QUEUES q, DBA_QUEUE_TABLES t
SEE
CODE DEPOT FOR FULL SCRIPT
q.QUEUE_TABLE = t.QUEUE_TABLE AND
q.OWNER = t.OWNER
/
A buffered queue consists of following two
storage areas:
-
System Global Area (SGA) memory associated with
a SYS.AnyData queue that contains only captured events
-
Part of a queue table for a SYS.AnyData queue
that stores captured events that have spilled from memory
A buffered queue helps to optimize the capture
of events by buffering them in the SGA instead of always storing
them in a queue table. This buffering of captured events occurs at
both the source database and the destination database. Captured
events are always stored in a buffered queue, but user-enqueued LCR
events and user-enqueued non-LCR events are always stored in queue
tables rather than in buffered queues.
To determine whether there are captured events
in a buffered queue, the v$buffered_queues and
v$buffered_subscribers dynamic performance views can be queried.
The latter view shows the Streams clients who subscribe to this
queue to receive the messages. Sometimes it is possible that more
than one destination database will receive the captured events. In
other words, there exists more than one subscriber to the queues
messages.
The above text is
an excerpt from:
Oracle Streams
High Speed Replication and Data
Sharing
ISBN 0-9745993-5-2
by Madhu Tumma
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