Errors in universe.log related to a missing MU

Document ID : KB000101492
Last Modified Date : 20/06/2018
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Issue:
User finds in universe.log massive amounts of error messages of the following kind:

|ERROR|X|IO |pid=p.t| owls_mu_read  | cannot read MU [MISSING_MU][G000000012], err=[3]
|ERROR|X|IO |pid=p.t| o_io_cache_data_provider_ | Error getting Mu <MISSING_MU>: 600

This MU is however no longer present on this Dollar Universe Instance because it has been already deleted.
Environment:
Any Dollar Universe Version can be impacted on any system.
Cause:
This MU has been deleted from this instance without verifying if it was used by other any task or session.

This can be verified either in Univiewer Console by displaying tasks and session and filtering on the name of the MU.

Another way can be via the command line 

$UNI_DIR_EXEC/uxshw tsk tsk=* mu="MISSING_MU"
or
%UNI_DIR_EXEC%/uxshw tsk tsk=* mu="MISSING_MU"
 
Resolution:
Look for this MU, either in Univiewer Console by displaying tasks and session and filtering on this MU, Or by the command line 

$UNI_DIR_EXEC/uxshw tsk tsk=* mu="MISSING_MU"

or

%UNI_DIR_EXEC%\uxshw tsk tsk=* mu="MISSING MU"

Delete the retrieved task or tasks if there are several one, or modify their MU and map it to a valid MU.
 
Additional Information:

Please note that this suggestion is a very probable reason for the problem but the issue can also be related to a "Session" where the "Execution Context" points to a missing MU or a Dependency pointing to a missing MU inside a Uproc.
Commands like: "uxshw upr upr=*" or "uxshw ses ses=* lnk" should indicate what is the guilty object.