CMMVC9579E Cannot remove a data reduction child pool with associated volumes.
Explanation
This error occurs when an attempt is made to remove a data reduction child pool when the pool still contains volumes or volume copies.
User response
Remove all associated volumes and volume copies from the data reduction child pool, and then use the rmmdiskgrp command without the -force parameter. Do not use the -force parameter with the rmmdiskgrp command to remove a data reduction child pool.