Administrator's Guide


Database and Recovery Log

The TSM database contains information needed for server operations and information about client data that has been backed up, archived, and space-managed. The database does not store client data. Instead, the database points to the locations of the client files in the TSM storage pools.

The database includes:

Note:If the database is unusable, the entire TSM server is unavailable. If a database is lost and cannot be recovered, the backup, archive and space-managed data for that server is lost. See Chapter 20, Protecting and Recovering Your Server for steps that you can take to protect your database.

The recovery log contains information about database updates that have not yet been committed. Updates can include activities such as defining a management class, backing up a client file, and registering a client node. Changes to the database are recorded in the recovery log to maintain a consistent database image.

How Tivoli Storage Manager Processes Transactions

To support multiple transactions from concurrent client sessions, the server holds transaction log records in the recovery log buffer pool until they can be written to the recovery log. These records remain in the buffer pool until the active buffer becomes full or TSM forces log records to the recovery log.

Changes resulting from transactions are held in the buffer pool temporarily and not made to the database immediately. Therefore, the database and recovery log are not always consistent. When all records for a transaction are written to the recovery log, TSM updates the database. The transaction is then committed to the database. At some point after a transaction is committed, the server deletes the transaction record from the recovery log.

How Space Is Managed by the Server

TSM tracks all volumes defined to the database as one logical volume and all volumes defined to the recovery log as another logical volume. In Figure 58, the database consists of four volumes: VOL1 through VOL4, which TSM tracks as a single logical volume.

Figure 58. A Server Database



A Server Database


To manage the database and recovery log effectively, you must understand the following concepts:

Available Space

Not all of the space that is allocated for the database or recovery log volumes can be used for database and recovery log information. TSM subtracts 1MB from each physical volume for overhead. The remaining space is divided into 4MB partitions. For example, you allocate four 25MB volumes for the database. For the four volumes, TSM requires 4MB for overhead leaving 96MB of available space as shown in the following figure:

Figure 59. An Example of Available Space



Available Space


Assigned Capacity

Assigned capacity is the available space that can be used for database or recovery log information. During installation, the database and recovery log assigned capacities match the available space.

If you add volumes after installation, you increase your available space. However, to increase the assigned capacity, you must also extend the database or recovery log. See Step 2: Extending the Capacity of the Database or Recovery Log for details.

Utilization

Utilization is the percent of the assigned capacity in use at a specific time. Maximum percent utilized is the highest utilization since the statistics were reset. For example, an installation performs most backups after midnight. Figure 60 shows that utilization statistics for the recovery log were reset at 9 p.m. the previous evening and that the maximum utilization occurred at 12 a.m.

Figure 60. An Example of Recovery Log Utilization



Recovery Log Utilization


Unless an unusually large number of objects are deleted, the database maximum percent utilized is usually close to the utilization percentage.


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