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100 IBM System Storage DS6000 Series: Copy Services with IBM System z
Incremental FlashCopy, Persistent FlashCopy, Change Recording option
Incremental FlashCopy operates at the full volume level. You can use Incremental
FlashCopy to create an initial point-in-time copy of a source volume and refresh the target
volume by copying only the changed data. After the initial full volume copy of the source
volume to the target volume, the FlashCopy relationship remains (persists) between the
source and target volume pair and the changes on the source and target volumes since
the last point-in-time copy are tracked. When you refresh the target volume at a new
point-in-time, only the changed tracks are copied.
The direction of the refresh can be reversed when you indicate that the original target now
becomes the source and the original source becomes the target.
You can use the FCINCREMENTAL keyword for a COPY FULL or COPY TRACKS
CPVOLUME operation to perform an initial full volume copy if no Incremental FlashCopy
relationship exists between the volume pair. If there is an existing Incremental FlashCopy
relationship between the volume pair, DFSMSdss will copy the changed tracks in the
(new) direction designated by the INDDNAME/INDYNAM and
OUTDDNAME/OUTDYNAM keywords. The new direction can be the same or the reverse
of the original (existing) direction.
You can use the FCINCREMENTALLAST keyword on the COPY FULL or COPY
TRACKS CPVOLUME commands to copy the changed tracks when there is an
Incremental FlashCopy relationship between the volume pair. FCINCREMENTALLAST
specifies that the new FlashCopy relationship will be nonpersistent and Change
Recording will be stopped after the final increment has been established. The FlashCopy
relationship will end when background copy for the final increment has completed.
You can use the FCINCRVERIFY(NOREVERSE | REVERSE) keyword to verify that the
existing Incremental FlashCopy direction is what you expected. DFSMSdss will fail the
copy attempt if the existing direction is not as expected.
When you reverse the direction of an Incremental FlashCopy, the storage facility requires
that the previous background copy has completed. You can specify the FCWAIT keyword
with a query interval value in seconds and a number of retries value to direct DFSMSdss
to wait for background copy completion before initiating the new Incremental FlashCopy.
No full volume background copy
It is possible to determine whether the data of the source volume should be copied to the
target volume in the background or not. If DFSMSdss uses the DS6000 FlashCopy, the
parameter FCNOCOPY is analyzed to determine whether a copy should take place or not.
If FCNOCOPY is specified, the FlashCopy relationship stays persistent and only updates
to the source are reflected in the target. If this parameter is omitted, then a physical copy
of the data is done in the background and the FlashCopy relationship is ended after all
data has been copied.
Change copy mode, no copy to full background copy
When an existing FlashCopy relationship is converted from no-background copy
(FCNOCOPY) to background copy mode, the relationship ends (unless the relationship is
persistent) when the background copy has completed.
You can change the existing FlashCopy copy mode by performing a physical full volume
or tracks copy specifying the FCNOCOPYTOCOPY keyword along with the source
volume or extents for which you want background copy to be started. The
FCNOCOPYTOCOPY function will initiate background copy of any NOCOPY FlashCopy
relationships in which the specified source volume or extents are participating.
In general, if you want a temporary copy of the data, specify FCNOCOPY and then
withdraw the FlashCopy relationship when you no longer need the copy. If you want a
permanent copy, but want to delay background copy until a convenient time, specify