ODA High SWAP Usage Without any Memory Pressure (Doc ID 2114474.1)

Last updated on MARCH 17, 2016

Applies to:

Oracle Database Appliance Software - Version 12.1.2.1 to 12.1.2.4 [Release 12.1]
Information in this document applies to any platform.

Symptoms

See high swap usage as shown by OS commands such as top, vmstat, proc/meminfo.

However, there is no memory pressure. There is plenty of free memory and memory in I/O cache that could be freed for user application requests.

 

proc/meminfo example

zz***Tue Feb 23 10:00:09 CET 2016
MemTotal: 98930208 kB
MemFree: 3308612 kB
Buffers: 730816 kB
Cached: 26348404 kB <<===== plenty of cache to be freed for user applications
SwapCached: 378856 kB
Active: 28909144 kB
Inactive: 3550216 kB
Active(anon): 23322644 kB
Inactive(anon): 810756 kB
Active(file): 5586500 kB
Inactive(file): 2739460 kB
Unevictable: 467044 kB
Mlocked: 467044 kB
SwapTotal: 19529196 kB
SwapFree: 8483108 kB <<===== swap used

 

vmstat example:


zzz ***Tue Feb 23 10:00:09 CET 2016
procs -----------memory---------- ---swap-- -----io---- --system-- -----cpu------
r b swpd free buff cache si so bi bo in cs us sy id wa st
6 1 11046088 3312228 730812 26348408 0 0 462 472 0 0 2 1 95 2 0 <<=================No swapping of blocks in/out despite high swap usage
1 0 11046088 3341960 730852 26303108 0 0 152 347 25265 18761 13 4 83 0 0
2 0 11046088 3340464 730852 26302824 0 0 285 1906 27261 20301 4 1 92 3 0

 

Cause

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