You have issued the DS Command-Line Interface (CLI) rmfbvol command with the safe parameter. This option runs a subtask that queries the user-defined volume groups to determine if the volume is assigned to a user-defined volume group. The query subtask has not completed successfully.
Wait a few minutes and resubmit the command, or resubmit the command without the safe option if you want to delete a volume without ensuring that it is not assigned to a user-defined volume group.