IBM System storage DS6000 Series Redbook page 134

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The main benefit of the DDSW(YES) parameter is that it can be used to easily free up tracks
on both the source and the corresponding target volumes that are in FlashCopy relationships
that are no longer needed because the original source data—that justified 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. More details on this subject can be found in
DFSMS Advanced Copy Services, SC35-0428.
Displaying information for volumes in a FlashCopy relationship
The TSO FCQUERY command is used to display available information about FlashCopy and
other copy services relationships active on the device. If the device is not in a source or target
FlashCopy relationship, the FCQUERY report shows the number of active FlashCopy
relationships as 0.
As shown in Example 9-24, the FCQUERY output report indicates that device 350A has one
active FlashCopy relationship (ACT=1) and is in a remote mirror session as a secondary
device (PC=S). The very same device is not in a z/OS Global Mirror session (XC=N), nor in a
Concurrent Copy (CC=N), and it has a nonrevertible status (RV=N).
Example 9-24 FlashCopy report - FCQUERY
FCQUERY DEVN(350A)
*******************************************************************************************
ANTF0420I FCQUERY Formatted -2
DEVN SSID LSS CCA CU SERIAL ACT MAX XC PC CC RV SEQNUM
420A 4200 02 0A 1750 0000000ABTV1 1 50099 N S N N 00000000
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IBM System Storage DS6000 Series: Copy Services with IBM System z