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Chapter 7. Copy Services 119
Figure 7-2 Incremental FlashCopy
In the Incremental FlashCopy operations:
1. At first, you issue full FlashCopy with the
change recording option. This option is for
creating change recording bitmaps in the storage unit. The change recording bitmaps are
used for recording the tracks which are changed on the source and target volumes after
the last FlashCopy.
2. After creating the change recording bitmaps, Copy Services records the information for
the updated tracks to the bitmaps. The FlashCopy relationship persists even if all of the
tracks have been copied from the source to the target.
3. The next time you issue Incremental FlashCopy, Copy Services checks the change
recording bitmaps and copies only the changed tracks to the target volumes. If some
tracks on the target volumes are updated, these tracks are overwritten by the
corresponding tracks from the source volume.
You can also issue incremental FlashCopy from the target volume to the source volumes with
the
reverse restore option. The reverse restore operation cannot be done unless the
background copy in the original direction has finished.
Data Set FlashCopy
Data Set FlashCopy allows a FlashCopy of a data set in a zSeries environment.
Source Target
Write
Read
Write
Read
Incremental FlashCopy
Initial FlashCopy
relationship established
with change recording and
persistent copy options
Control bitmap for each
volume created
Tracks changed on the
target are overwritten by
the corresponding tracks
from the source
Possible reverse operation,
the target updates the
source
Incremental FlashCopy
started
Tracks changed on the
source are copied to the
target