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Primary Note for AQ Queue Monitor Process (QMON) (Doc ID 305662.1)

Last updated on JANUARY 17, 2023

Applies to:

Oracle Database Backup Service - Version N/A and later
Oracle Database Cloud Exadata Service - Version N/A and later
Oracle Database Cloud Service - Version N/A and later
Oracle Database - Standard Edition - Version to [Release 9.2 to 11.2]
Oracle Database - Enterprise Edition - Version to [Release 8.1.7 to 12.1]
Information in this document applies to any platform.


In this article, we will discuss the following

1. The Queue Monitor Coordinator process (QMNC) , the Queue Monitor Server Processes (QXXX) and Task Operations which can be assigned to these processes. Collectively these processes are named the Queue Monitor processes or QMON processes.

2. Known issues which affect these processes.

3. How to collect useful diagnostic information when problems arise with them.


Database administrators of Advanced Queueing (AQ) and Streams databases.


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In this Document
 Queue Monitor Processes - QMON
 Pre-10.1 QMON Architecture
 10.1 onwards QMON Architecture
 QMON coordinator
 QMON tasks
 QMON Server Processes
 Significance of the AQ_TM_PROCESSES Parameter in 10.1 onwards
 Common Observations / Issues linked to QMON
 PROCESSED Messages not being removed
 TM Operations : Delay, Expiration, Retention not working as expected
 Delay / WAIT Period Incorrect after Daylight Saving Time change
 High CPU usage from QMON Coordinator process
 Unexpected Growth in Queue Table Objects
 QMON Space Reclamation / Coalesce Queues
 Collecting Diagnostic Information for Troubleshooting QMON issues

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