Tivoli Storage Manager for Windows: Administrator's Guide


Overview of Volumes

Administrators are responsible for managing tape and optical disk media, as well as managing the logical data on the media. TSM represents both the media and the data in a construct called a storage pool volume. Each storage pool volume is equivalent to a tape or an optical disk.

TSM has two ways of classifying volumes:

Scratch Volumes
Scratch volumes are labeled volumes that can be used to satisfy any tape mount request. When TSM writes data to a scratch volume, its status is changed to private. When valid data has been reclaimed from the volume, it is returned to scratch status. A scratch volume is either empty, or contains only invalid data.

Private Volumes
Private volumes are labeled volumes that can only be mounted when specified by name. You can specify private status for a given volume, or private status can be specified by TSM as it writes data to scratch volumes. A private volume can be empty, or it can contain valid or invalid data.

TSM tracks the status of tape and optical disk volumes to determine whether they are scratch or private.

TSM Volume Processing

When TSM selects a volume for a backup, it attempts to first locate a partially-written volume, if one exists. If no partially-written volumes are found, TSM requests a scratch volume. TSM has no knowledge of scratch volumes until they are selected. Once a volume is mounted, TSM records the original status of the volume. After TSM has written to a volume, it modifies the status to private. Thus, all partially-written volumes are private volumes, regardless of their original status. TSM knows only about private volumes and partially-written volumes. Partially-written volumes are volumes that TSM marked as private when data was backed up.

Note:
TSM does not try to keep backups for the same client or client file space together on volumes unless collocation is enabled. For more information, see Keeping a Client's Files Together: Collocation.

Defining Volumes

Any tape or optical disk is a candidate to become a TSM volume. TSM volumes are defined when you create the storage pools for the devices. When you add devices with the Device Configuration Wizard, the wizard automatically creates a storage pool for each device it configures and allows a maximum of 500 scratch volumes for the storage pool. When you add devices with TSM commands, you specify the maximum number of scratch volumes with the MAXSCRATCH parameter of the DEFINE STGPOOL or UPDATE STGPOOL command. If the MAXSCRATCH parameter is 0, all the volumes in the storage pool are private volumes. If the MAXSCRATCH parameter is greater than zero, all of the volumes in the storage pool are scratch volumes.

For example, to create a storage pool named STORE1 that can use up to 500 scratch volumes, enter the following:

define stgpool store1 maxscratch=500

For each storage pool, decide whether to use scratch volumes or private volumes. Scratch volumes are recommended for the following reasons:

Private volumes require much more human intervention than scratch volumes. However, you may need to regulate the volumes used by individual storage pools, and want to manually control the volumes. You will trade the additional human intervention for absolute control over volumes. In these situations, you must define each private volume with the DEFINE VOLUME command. To mount private volumes, you must provide the volume names. For database backups, dumps, or loads, or for server import or export operations, you must list the private volumes.

Managing Volumes

When TSM requires a new volume, it chooses the volume from the storage pool available for client backups. If you set up private volumes, TSM selects a specific volume. If you set up scratch volumes, TSM selects any scratch volume in the library. This is true for all devices except 3494 devices. See Managing Category Numbers for 3494 Library Devices.

Managing Partially-Written Volumes

TSM is unaware of a scratch volume until after the volume is mounted. Then, its status is changed to private and the volume is automatically defined as part of the storage pool for which the mount request was made. Partially-written volumes are always private volumes, even if their status was scratch before they were selected. TSM tracks the original status of scratch volumes, so it can return them to scratch status when they become empty.

For information on changing the status of a volume in an automated library device, see Modifying the Status of Automated Library Volumes.

Managing the Volume Inventory for an Automated Library Device

TSM maintains a volume inventory for each automated library device. The volume inventory allows the device to provide maximum automation. The volume inventory is created when you check media volumes into the library device. TSM tracks the status of volumes in the inventory as either scratch or private.

A list of volumes in the library volume inventory would not necessarily be identical to a list of volumes in the storage pool inventory for the device. For example, scratch volumes may be checked in to the library device but not defined to a storage pool because they have not yet been selected for backup; private volumes may be defined to a storage pool, but not checked into the device's volume inventory.

Managing Database Backup and Database Export Volumes

For database backup and database export volumes, issue the DELETE VOLHISTORY command or the UPDATE LIBVOLUME command to change the status of the volume.

When TSM backs up the database or exports server information, TSM records information about the volumes used for these operations in the volume history file. Volumes that are tracked in the volume history file require you to delete the volume information from the volume history file. The volume history file is a key component of server recovery and is discussed in detail in Chapter 23, Protecting and Recovering Your Server.


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