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Don Burleson Blog 







  AQ Background Master: slave start wait tips

Oracle Database Tips by Donald BurlesonApril 14, 2015

Question:  In Oracle 12c I am seeing AQ Background Master: slave start waits.  What is the AQ Background Master: slave start wait? 

Answer: Good question!  Sadly, this wait event is new and undocumented.

Oracle 12c has the AQ Background Master: slave start wait event is associated with the QMON background tasks (i.e. QM02).   The Queue Monitor Coordinator QMNC background task  is responsible for facilitating various background activities required by Advanced Queuing (AQ) and Oracle Streams, spawning factotum (slave) processes named Qnn.  Collectively, QMNC and Q01, Q02, etc. are referred to as the QMON background processes. 

Here are the 12c AQ wait events, associated with any Qnn processes:

  • AQ Background Master: slave start
  • AQ Cross Master idle
  • AQ master shutdown
  • AQ master: time mgmt/task cleanup
  • AQ propagation connection
  • AQ reload SO release
  • AQ slave: time mgmt/task cleanup
  • AQ spill debug idle
  • AQ: 12c message cache init wait
  • AQ: non durable subscriber add or drop

The name itself implies that this is a advanced queuing background process, staring a factotum (slave) process, ostensibly to process the queues.

This wait event is not documented and very little is known about it as of this date.

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