As I understand, AIX takes memory that's not used for AIX itself or the application for file caching.
I use nmon "m".
For an explanation of the AIX virtual memory manager see Overview of AIX page replacement
or this Practical Guide to AIX
For an explanation of some nmon memory values see https://www.stix.id.au/wiki/Tuning_the_AIX_file_caches
or AIX memory statistics
To check for memory overcommitment, I check the following values:
PageSpace shows the usage of the paging spaces
pages/sec to Paging Space (to File System means normal file I/O that is handled by the memory manager too)
Page Scans: how often must AIX check to find free pages (higher percentage is bad)
Page Steals : high number means memory conention (is bad).
lruable pages: how many pages can be examined by the least recently used scan (high number = good).
The numclient (jfs2), maxclient (jfs2) values show the usage of memory for file caching.
As far as I understand, numperm = numclient (JFS2+NFS cache) + client pages (jfs Cache)
If nmon shows higher values of "to Paging Space", "Page Scans" or "Page Steals", I would go deeper in detail with the mentioned AIX commands.
BTW: if you find a process "/usr/bin/topasrec", it's the longterm recording of nmon, you will find its output in
/etc/perf/daily or /var/perf/daily.
The output must be processed by topasout directly or with parameter -a that generates files for the nmon analyzer
see https://developer.ibm.com/technologies/systems/articles/au-nmon_analyser/
with a link to the download site (nmon.sourceforge.net).
You download and open the files created by topasrec in EXCEL, then longterm usage of memory could be seen (good to detect spikes in the nightshift).
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Achim Haag
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Original Message:
Sent: Tue June 25, 2019 04:47 PM
From: Archive User
Subject: Re: High Memory Utilization in AIX 7.1
Originally posted by: Tarcio Nieri
I have a similar problem.
I see in topas, the processes that most consume memory, and as always java is between them. However the amount of memory used by them does not justify the result I see in nmon, which says that more than 90% of memory is being used.