5C6

Explanation
When the system detects an error in internal WebSphere® MQSeries® processing, it will abnormally
end a connected user task (TCB) or one of its own internal tasks.
  See    WebSphere MQ  for
a description of diagnostic approaches to either a X'5C6' or X'6C6' abend and for information about the reason codes associated
with either abend. .

System action
The system abnormally ends the connected user
task or the MQSeries internal
task.

System programmer response
If the error recurs and the program
is not in error, look at the messages in the job log for more information.
 Search problem reporting databases for a fix for the problem.  If
no fix exists, contact the IBM® Support
Center.  Provide the SYSOUT output for the job and the logrec data
set error record.

Programmer response
Check register 15 of the SDWA section 'General
Purpose Registers at Time of Error', and locate the accompanying reason
code.  In addition, check the information displayed at the console
screen, and in the corresponding logrec data set entry.

Source
MQSeries