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Administrator's Guide
Tivoli Storage Manager allows you to control how removable media are used
and reused. After Tivoli Storage Manager selects an available medium,
that medium is used and eventually reclaimed according to its associated
policy.
Tivoli Storage Manager manages the data on the media, but you manage the
media itself, or you can use a removable media manager. Regardless of
the method used, managing media involves creating a policy to expire data
after a certain period of time or under certain conditions, move valid data
onto new media, and reuse the empty media.
In addition to information about storage pool volumes, the volume history
contains information about tapes used for database backups and exports (for
disaster recovery purposes). The process for reusing these tapes is
slightly different from the process for reusing tapes containing client data
backups.
Figure 5 shows a typical life cycle for removable media. The
numbers (such as (1)) refer to numbers in the figure.
Figure 5. Simplified View of the Life Cycle of a Tape

- You label (1) and check in (2) the media.
Checking media into a manual library simply means storing them (for example,
on shelves). Checking media into an automated library involves adding
them to the library volume inventory.
See Labeling Removable Media Volumes.
- If you plan to define volumes to a storage pool associated with a device,
you should check in the volume with its status specified as private.
Use of scratch volumes is more convenient in most cases.
- A client sends data to the server for backup, archive, or space
management. The server stores the client data on the volume.
Which volume the server selects (3) depends on:
- The policy domain to which the client is assigned.
- The management class for the data (either the default management class for
the policy set, or the class specified by the client in the client's
include/exclude list or file).
- The storage pool specified as the destination in either the management
class (for space-managed data) or copy group (for backup or archive
data). The storage pool is associated with a device class, which
determines which device and which type of media is used.
- Whether the maximum number of scratch volumes that a server can request
from the storage pool has been reached when the scratch volumes are
selected.
- Whether collocation is enabled for that storage pool. When
collocation is enabled, the server attempts to place data for different
clients or client nodes on separate volumes. For more information, see Keeping a Client's Files Together: Collocation.
See Figure 6.
Figure 6. How Tivoli Storage Manager Affects Media Use

- The data on a volume changes over time as a result of:
- Expiration of files (4) (affected by management class and copy
group attributes, and the frequency of expiration processing). See Basic Policy Planning.
- Movement and deletion of file spaces by administrator
- Automatic reclamation of media (5)
The amount of data on the volume and the reclamation threshold set for the
storage pool affects when the volume is reclaimed. When the volume is
reclaimed, any valid, unexpired data is moved to other volumes or possibly to
another storage pool (for storage pools with single-drive
libraries)..
- Collocation, by which Tivoli Storage Manager attempts to keep data
belonging to a single client node or a single client file space on a minimal
number of removable media in a storage pool.
If the volume becomes empty because all valid data either expires or is
moved to another volume, the volume is available for reuse (unless a time
delay has been specified for the storage pool). The empty volume
becomes a scratch volume if it was initially a scratch volume. The
volume starts again at step 3.
- You determine when the media has reached its end of life.
For volumes that you defined (private volumes), check the statistics on the
volumes by querying the database. The statistics include the number of
write passes on a volume (compare with the number of write passes recommended
by the manufacturer) and the number of errors on the volume.
You must move any valid data off a volume that has reached end of
life. Then, if the volume is in an automated library, check out the
volume from the library. If the volume is not a scratch volume, delete
the volume from the database.
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