Reclamation Of Copy Exported Physical Volumes - IBM TS7700 Series User Manual

August 15, 2017

Reclamation of Copy Exported Physical Volumes

Even though a copy exported physical volume has been ejected from a source TS7700 and taken to another
location, the source TS7700 continues to perform space management for them. Their active data content is
tracked just like any other physical volume in the TS7700. As the primary logical volumes in the source
TS7700 are modified, returned to scratch and deleted or ejected from the library, and thus resulting in a
reduction in the amount of active data on the physical volumes in the primary physical volume pool, the
same is done for the secondary copies that are on copy exported physical volumes assigned to a secondary
physical volume pool. Offsite reclamation of the secondary copies only adheres to the reclamation threshold
requirements for establishing which volumes are eligible for reclamation. Other reclamation settings (Days
without Access, Age of Last Data Written, Days without Data Inactivation and Maximum Active Data) do
not apply to offsite reclamation. In addition to becoming eligible for reclamation because a copy exported
volume meets the reclaim threshold criteria, you can make a copy exported volume eligible for priority
reclaim by using the host console request function, Library Request. Using that request, you would specify
the keywords COPYEXP,yyyyyy,RECLAIM; where yyyyyy is the volser of the copy exported volume you
want to reclaim.
Every 10 minutes, the TS7700 checks to see if there are any copy exported volumes that have been made
eligible for reclaim. If it finds one, it will begin to reclaim that volume. Reclaim through the Library
Request function is issued at a higher priority than normal reclaim processing and ignores the inhibit reclaim
schedule. Remember that normal reclaim processing does not check the ratio between active data size and
media capacity but check if the ratio between active data size and total bytes written to the physical volume
with reclaim threshold percent.
Note: If you wish to only have a copy exported physical volume become eligible for reclaim through the
Library Request function, you would need to make sure the reclaim threshold definitions for the pool
associated with the volumes are all set to 0, including the reclaim percentage.
Physical volumes exported with copy export that become eligible for reclaim are not brought back to the
source TS7700 to be reclaimed. Instead, the source TS7700 performs the following steps (This is called
Offsite Reclaim):
• Confirm that Copy Export is not running on the source TS7700 because reclamation of copy exported
physical volumes does not start while Copy Export is running.
• The source TS7700 determines which logical volumes on the exported physical volume are still valid.
•
For each of the valid logical volumes, it uses the primary copy of the volume as the source for the
reclaim, recalling it into cache and then migrating it to a physical volume associated with the secondary
volume pool the exported stacked volume is also associated with. As with any reclaim, the logical
volume's record in the TS7700 database is updated to indicate the new location of the secondary copy of
the volume. This also results in the amount of valid data on the exported physical volume being
reclaimed to decrease, eventually reaching zero when all of the valid logical volumes have been
processed.
• The maximum number of drives used for migrating logical vlumes to create secondary copy at Offsite
Reclaim is limited by the Maximum Devices of the copy export pool defined by the MI Pool Properties.
• Limit the number of exported physical volumes Offsite Reclaim processes at a time is 10 or fewer at the
code level earlier than 8.30.1.15. At the code level 8.30.1.22 or later, Offsite Reclaim processes exported
physical volumes one by one in the ascending order of active data size recorded on them.
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