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Administrator's Guide


Managing the Volume Inventory

With TSM, you manage your volume inventory by performing the following tasks:

Controlling Access to Volumes

TSM expects to be able to access all volumes it knows about. For example, TSM tries to fill up tape volumes. If a volume containing client data is only partially full, TSM will later request that volume be mounted to store additional data. If the volume cannot be mounted, an error occurs.

To make volumes that are not full available to be read but not written to, you can change the volume access mode. For example, use the UPDATE VOLUME command with ACCESS=READONLY. The server will not attempt to mount a volume that has an access mode of unavailable.

If you want to make volumes unavailable to send the data they contain offsite for safekeeping, a more controlled way to do this is to use a copy storage pool. You can back up your primary storage pools to a copy storage pool and then send the copy storage pool volumes offsite. You can track these copy storage pool volumes by changing their access mode to offsite, and updating the volume history to identify their location. For more information, see Backing Up Storage Pools.

Reusing Tapes in Storage Pools

To reuse tapes in storage pools, you must do two things:

Expiration Processing of Client Files
Expiration processing deletes from the database information about any client files that are expired (no longer valid according to the policies you have set). For example, suppose four backup versions of a file exist in server storage, and only three versions are allowed in the backup policy (the management class) for the file. Expiration processing deletes information about the oldest of the four versions of the file. The space that the file occupied in the storage pool can then be reclaimed.

You can run expiration processing automatically or by command. See Running Expiration Processing to Delete Expired Files.

Reclamation of Volumes
You can have TSM reclaim volumes that pass a reclamation threshold, a percentage of unused space on the volume. TSM moves data to consolidate valid, unexpired files onto fewer tapes. The reclamation threshold is set for each storage pool. See Reclaiming Space in Sequential Access Storage Pools.

For a storage pool associated with a library that has more than one drive, the reclaimed data is moved to other volumes in the same storage pool. For a storage pool associated with a library that has only one drive, the reclaimed data is moved to volumes in another storage pool that you must define, called a reclamation storage pool. See Reclaiming Volumes in a Storage Pool with One Drive.

Setting Up a Tape Rotation

Over time, media ages, and the data on backup may no longer be needed. You can reclaim useful data on media and then reclaim and reuse the media themselves. When you set up expiration processing, you can determine when data is no longer needed. See File Expiration and Expiration Processing.

TSM policy determines how many backup versions are retained and how long they are retained. See Basic Policy Planning.

Deleting Data - Expiration Processing
Expiration processing deletes data that is no longer valid either because it exceeds the retention specifications in policy or because users or administrators have deleted the active versions of the data. See Running Expiration Processing to Delete Expired Files.

Reusing Media - Reclamation Processing
Data on tapes may expire, move, or be deleted. Reclamation processing consolidates any unexpired data by moving it from multiple volumes onto fewer volumes. The media can then be returned to the storage pool and reused.

You can set a reclamation threshold that allows TSM to reclaim volumes whose valid data drops below a threshold. The threshold is a percentage of unused space on the volume and is set for each storage pool. The amount of data on the volume and the reclamation threshold for the storage pool affects when the volume is reclaimed. See Reclaiming Space in Sequential Access Storage Pools.

Determining When Media Have Reached End of Life
You can use TSM to display statistics about volumes including the number of write operations performed on the media and the number of write errors. TSM overwrites this statistical data for media initially defined as scratch volumes each time the media are reclaimed. For media initially defined as private volumes, TSM maintains this statistical data, even as the volume is reclaimed. You can compare the information with the number of write operations and write errors recommended by the manufacturer.

Reclaim any valid data from volumes that have reached end of life. If the volumes are in automated libraries, check them out of the volume inventory. Delete private volumes the database with the DELETE VOLUME command. See Reclaiming Space in Sequential Access Storage Pools.

Ensuring Media are Available for the Tape Rotation
Over time, the demand for volumes may cause the storage pool to run out of space. You can set the maximum number of scratch volumes high enough to meet demand by doing one or both of the following:

For automated libraries, see Managing Server Requests for Media.

Write-once-read-many (WORM) drives can waste media when TSM cancels transactions because volumes are not available to complete the backup. Once TSM writes to WORM volumes, the space on the volumes cannot be reused, even if the transactions are canceled (for example, if a backup is canceled because of a shortage of media in the device).

Large files can cause even greater waste. For example, consider a client backing up a 12GB file onto WORM platters that hold 2.6GB each. If the backup requires five platters and only four platters are available, TSM cancels the backup and the four volumes that were written to cannot be reused.

To minimize wasted WORM media:

  1. Ensure that the maximum number of scratch volumes for the device storage pool is at least equal to the number of storage slots in the library.
  2. Check enough volumes into the device's volume inventory for the expected load.

If most backups are small files, controlling the transaction size can affect how WORM platters are used. Smaller transactions mean that less space is wasted if a transaction such as a backup must be canceled. Transaction size is controlled by a server option, TXNGROUPMAX, and a client option, TXNBYTELIMIT.

Reusing Volumes Used for Database Backups and Export Operations

When you back up the database or export server information, TSM records information about the volumes used for these operations in the volume history file. TSM will not allow you to reuse these volumes until you delete the volume information from the volume history file. To reuse volumes that have previously been used for database backup or export, use the DELETE VOLHISTORY command. For information about the volume history file, see Saving the Volume History File.

Note:
If your server is licensed for the DRM product, the volume information is automatically deleted during MOVE DRMEDIA command processing. For additional information about DRM, see Chapter 23, Using Tivoli Disaster Recovery Manager.

Maintaining a Supply of Scratch Volumes

When you define a storage pool, you must specify the maximum number of scratch volumes that the storage pool can use. TSM automatically requests a scratch volume when needed. When the number of scratch volumes that TSM is using for the storage pool exceeds the maximum number of scratch volumes specified, the storage pool can run out of space.

Ensure that you set the maximum number of scratch volumes high enough for the expected usage. When you exceed this number, you can do one or both of the following:

For automated libraries, see also Maintaining a Supply of Scratch Volumes in an Automated Library.

Maintaining a Supply of Volumes in a WORM Library

For libraries with WORM drives, prevent cancellation of data storage transactions by maintaining a supply of scratch or new private volumes in the library. Canceled transactions can cause wasted WORM media. TSM cancels (rolls back) a transaction if volumes, either private or scratch, are not available to complete the data storage operation. After TSM begins a transaction by writing to a WORM volume, the written space on the volume cannot be reused, even if the transaction is canceled.

For example, if a client starts to back up data and does not have sufficient volumes in the library, TSM cancels the backup transaction. The WORM volumes to which TSM had already written for the canceled backup are wasted because the volumes cannot be reused. Suppose that you have WORM platters that hold 2.6GB each. A client starts to back up a 12GB file. If TSM cannot acquire a fifth scratch volume after filling four volumes, TSM cancels the backup operation. The four volumes that TSM already filled cannot be reused.

To minimize cancellation of transactions, do the following:


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