QMON Slaves Processes Consuming High Amount of CPU on 184.108.40.206
(Doc ID 1615165.1)
Last updated on JULY 28, 2020
Applies to:Oracle Database - Enterprise Edition - Version 220.127.116.11 and later
Oracle Database Exadata Cloud Machine - Version N/A and later
Oracle Cloud Infrastructure - Database Service - Version N/A and later
Oracle Database Exadata Express Cloud Service - Version N/A and later
Oracle Database Cloud Exadata Service - Version N/A and later
Information in this document applies to any platform.
You have observed that qmon slave processes (qXXX) are consuming a high amount of CPU.
To determine if you are suffering this problem, the following conditions should be met.
1) In AQ HC script (provided on Doc ID 1193854.1) html output, you can see :
a) At Statistics --> QMON section, the process consuming CPU are in status RUNNING and the task assigned are related to spilling like : QMON_SPILL or QMON_DEALLOC_SPILLED.
It can be idenfied using the following query too:
b) At Statistics --> Queues --> Buffered, there are buffered queues, but there are not buffered messages to spill:
num_msgs, spill_msgs, waiting, ready, expired, cnum_msgs, cspill_msgs, expired_msgs,
from gv$buffered_queues, gv$aq
order by 1,2,3;
2) A 10046/SQL trace for qmon slaves consuming cpu shows continous waits on 'library cache: mutex X' for the same idn all the time.
This issue has been observed on customer running EBS Workflow module, but can be observed on any type of queues.
It is more frequent to observe this issue on environment with ASMM (sga_target > 0) is being used and streams_pool_size parameter is not defined.
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