Using DDSW(YES)

The FCWITHDR command with the deleted data space withdraw (DDSW) parameter, when issued against an entire source volume, removes all target extents on the specified source device from their associated FlashCopy® relationships. In addition, any FlashCopy NOCOPY source tracks on the specified source device are changed to COPY (background copy) source tracks. This process causes all source tracks to be copied to their respective target tracks and all FlashCopy relationships to be removed from the specified source device. For additional information about how to restrict DDSW processing to selected portions of a volume, see Limiting the scope of a withdraw using the XTNTLST.

A FlashCopy withdraw with DDSW(YES) issued to the source of a relationship will cause a background copy to be initiated. It is not allowed if there is a space efficient target volume. The background copy will be initiated for any source relationships where the target is a fully provisioned volume, and then the command will receive a failing return code or error message because of the space efficient relationship.

The main benefit of the DDSW(YES) parameter is that it can be used to easily free up tracks on both the source and corresponding target volumes that are in existing FlashCopy relationships which are no longer needed because the original source data justifying the relationship has been deleted. Another example might be that prior to starting a backup cycle using DFSMSdss, you might want to make sure that all relationships have been cleaned up on the subject source volume.

However, if there is a space efficient target volume, you can not issue a FlashCopy withdraw with DDSW(YES) to the source of a relationship because the withdraw initiates the background copy.

Figure 1 illustrates the sequence of events that occur when the ESS removes target FlashCopy relationships that result when a FCWITHDR with DDSW(YES) command processes.

Figure 1. How the ESS processes the FCWITHDR with DDSW(YES) command

FCWITHDR SDEVN(ssss) DDSW(YES)

 1 

All target tracks on the source volume A are removed from their associated FlashCopy relationships (volume C and volume E).

 2 

For FlashCopy relationships that were established between the source volume A and target volumes (volume B and volume E) using the NOCOPY mode, the following occurs:

1. All FlashCopy source tracks are changed to COPY (background copy) source tracks.
2. The tracks are physically copied to their respective target tracks.
3. When the background copies are complete, all FlashCopy relationships are removed.

 3 

A FlashCopy relationship that was established between the source volume A and the target volume D using the COPY mode is allowed to complete. The FlashCopy relationship is removed automatically when the copy completes.