WARNING: Heavy swapping observed on system in last 5 mins.

APPLIES TO:

Oracle Database – Enterprise Edition – Version 11.2.0.3 and later
Information in this document applies to any platform.

GOAL

The document explains why you may see the following WARNING in the alert log after upgrading to 11.2.0.3.

SOLUTION

The reason you may now see these informational messages in the alert is due to the fact that in 11.2.0.3 an enhancement fix was included for unpublished Bug 10220118.
Please refer to
Note 10220118.8 - Bug 10220118 – Print warning to alert log when system is swapping

Description

  This fix is really an enhancement.
  With this fix a warning is printed to the alert log (and DBRM trace)
  if excessive swapping is observed on the system.
  The warning will not be printed more than once per hour.
  

The same issues could have been happening on 11.2.0.2 but they simply would not have been reported.
There is no (immediate) cause for concern and we suggest that the databases are just monitored as usual.

If you look in the alert log, you will see that the message does not happen every hour. 
If SWAP was causing any serious issue we could also see ORA-4031/ORA-4030 and would then be able to use the DBRM trace in conjunction with obtaining further diagnostics.
 

AIX Platform

If your Platform is IBM-AIX then this is not the only possible reason for this alert log message. 
For IBM AIX on POWER Systems (64-bit), there is also next known port-specific bug:
Bug 14731911 - FALSE SWAP WARNING MESSAGES PRINTED TO ALERT.LOG ON AIX
with unpublished base bug:
Bug 11801934 : WRONG PAGE-IN AND PAGE-OUT OS VM STATS IN AIX.
 

VMWare

Under VMWare, the messages may perhaps indicate a more serious issue, even when no memory related ORA-4031/ORA-4030 errors are reported. 
Under circumstances, an instance in a virtual machine may be simply terminated by PMON due to error 471 without further errors in the alert log.
The OS logs may in such case report an out of memory condition like below:

SOLUTION

General solution:
o  Avoid the memory pressure by either providing more memory or decreasing the need for (shared) memory for the Oracle instance(s).

For AIX:
o  Apply interim Patch 11801934 if available for your Oracle version or request a patch with Oracle Support in a new Service Request.