CMMVC6976E The command cannot be initiated because the MDisk has an array parity rebuild ongoing.

Explanation
This error can occur when an attempt is made to run a command while an array is not synchronized
because data is being rebuilt during a copyback process.

User response
Wait until the data is rebuilt, and then retry the command. You can use the
lsarraysyncprogress command to view the progress of the synchronization.