There may be times when you expect DFSMSdss to use SnapShot to move the data but SnapShot was not used. As far as you can tell, your volume meet all the criteria for SnapShot use. Use the DEBUG(FRMSG(MINIMAL | SUMMARIZED | DETAILED)) keyword to help you resolve this situation. Include this keyword to indicate the applicable fast replication message level (MIN, SUM, or DTL) in your DEFRAG command. The message level controls the type and amount of information that DFSMSdss provides.

DEBUG(FRMSG(MIN | SUM | DTL)) directs DFSMSdss to issue an informational message that indicates why SnapShot was not used. When you specify FASTREPLICATION(REQUIRED), the informational message is issued in addition to the ADR938E message whether you have specified the DEBUG(FRMSG(MIN | SUM | DTL)) keyword or not.

For more information about the DEBUG(FRMSG(MIN | SUM | DTL)) keyword, refer toz/OS DFSMSdfp Storage Administration.