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Excessive PGA memory usage by the Wnnn Background Process (Doc ID 2685491.1)

Last updated on JUNE 30, 2020

Applies to:

Oracle Database - Enterprise Edition - Version 12.1.0.2 and later
Information in this document applies to any platform.

Symptoms

Each Wnnn Background Process is consuming around 140MB of pga ( can be more as well) and holding hundreds of opened cursors causing memory usage of instance to go high.
The sessions appear to remain open (session state ACTIVE), holding these cursors.

The Wnnn and SMCo processes appear to remain active for weeks at a time, as we can seen by logon time.

Example pga use of one affected instance:

Summation of PGA based on v$process:
------------------------

Mbytes allocated Mbytes used
---------------- -----------
5621.75582 4601.06588

The processes that contribute to more pga usage on instance is Wnnn ( space management slave processes).
There are 16 Wnnn processes using 140MB of PGA.

PROCESS CONSUMING MORE PGA:( example details)
------------------------

LOGON SID SERIAL# SPID PGA_MB_USED USERNAME STATUS OSUSER MACHINE PROGRAM MODULE
---------- ---------- ---------- ---------- ----------- ---------- -------- ------- ---------- -------- ---------------
215 Days + 1221 3553 8581 155.5 ACTIVE oracle hostname oracle@instancename KTSJ (W000)
14:05:27

215 Days + 743 56880 9117 146.42 ACTIVE oracle hostname oracle@instancename KTSJ (W006)
14:02:14

215 Days + 738 55952 10241 145 ACTIVE oracle hostname oracle@instancename KTSJ (W00D)
13:55:01

215 Days + 1477 40129 9123 144.61 ACTIVE oracle hostname oracle@instancename KTSJ (W009)
14:02:06

215 Days + 15 30316 9114 142.7 ACTIVE oracle hostname oracle@instancename KTSJ (W005)
14:02:18

215 Days + 498 14753 8701 142.33 ACTIVE oracle hostname oracle@instancename KTSJ (W004)
14:05:06
.
.
.



Cause

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In this Document
Symptoms
Cause
Solution
References


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