3.2 Monitoring and Managing TSM Database and Recovery log space usage


1) You have to create and designate directories or drives that the server uses for the database during TSM Server instance configuration. Afterward, the database manager, which is part of the server, automatically manages the space available to the directories as database space.

2) Locate the database on fast reliable storage, such as Redundant Array of Independent Disks (RAID) hardware. Do not place the database in directories that might run out of space. Locate the directories across different physical devices (separate LUNs).

3) Database size is determined by the amount of data that you store. The Database Manager manages the database space automatically. The maximum supported limit is 4 TB. Use the QUERY DBSPACE command to monitor database space usage. The size of the database depends on the following factors
  • The number of client files to store
  • The number of versions of backed up files that are kept
  • Whether you use caching
4) Caching option is available in the disk storage pool. When cache is enabled, the migration process leaves behind duplicate copies of files after the server migrates these files to the next storage pool in the hierarchy. Consider using Active Data Pools instead.

Also Read: Is it required to rebalance the TSM Server DB tablespaces after adding the new db filesystem ? 

5) There are both advantages and disadvantages of enabling cache on disk pools. You need to cheese this option according to your resources. Using cache can improve the speed with which the server retrieves some files. Consider enabling cache for space-managed files that clients frequently access. If space is needed to store new data in the disk storage pool, cached files are erased and the space is used for those new files.
  • Using cache can require more space for the server database because the server maintains two copies of the file.
  • If you want to use caching, you cannot also enable shredding for that disk storage pool.

TSM Database size estimation:

The size of your Tivoli Storage Manager database depends on the number of client files to store and how Tivoli Storage Manager manages them. If you can estimate the maximum number of files that might be in server storage at any time, you can use the following information to come up with a useful database size estimate.

Also Read: Use this DB2 command to extend TSM DB space when the TSM server is down or unable to startup
  • Each version of a file that Tivoli Storage Manager stores requires about 400 to 600 bytes of database space.
  • Each cached or storage pool copy of a file requires about 100 to 200 bytes of database space. Caching is turned off by default. It is used only to move from one storage pool to next.
  • Overhead can increase the required space by an additional 50%.

Maximum and Minimum size allowed for Database and Recovery log

Database
  • Minimum size: 2.2 GB
  • Maximum size: 4 TB
Consider restore time when deciding how large the database should be. 

Active log
  • Minimum size: 2 GB
  • Maximum size: 128 GB
  • Default size: 16 GB
Active log space requirements increase when you use data deduplication. 

Archive log
  • Large enough to contain the logs that the previous full backup generates
  • Cleared only in the case of a full backup

Example for Database estimation

  • Backed up objects
50,000,000 objects might be backed up. Storage policies call for retaining up to three copies of backed up files. 150,000,000 stored backed up objects.
  • Archived objects
10,000,000 objects might be archived copies of client files.
  • Space-managed objects
20,000,000 objects migrated from client workstations might be in server storage. [(50,000,000 X 3 ) + 10,000,000 + 20,000,000)] x 600 bytes = 100 GB
  • Copy storage pool objectsAll primary storage pools are backed up to the copy storage pool:
(150,000,000 + 10,000,000 + 20,000,000) x 200 bytes = 34.3 GB 
  • Active-data pool objectsAll the active client backup data in primary storage pools is copied to the active-data pool. 
Assume that 50,000,000 versions of the backup files in the primary storage pool are active.
50,000,000 x 200 bytes = 9.5 GB

Estimated database size: 144 GB + overhead (up to 50%) = approximate 216 GB

In the above example, the computations represent probable maximums. The numbers are not based on the use of file aggregation. In general, the more that small files are aggregated, the less database space that is required.

If you cannot estimate the numbers of files, you can roughly estimate the database size as 1% to 5% of the required server storage space. For example, if you need 1,000 GB of server storage, make your database between 10 GB and 50 GB.

Increasing the TSM V7 Database Size

1) You can add directories to the database by using the EXTEND DBSPACE command. The updates for this operation include distributing data across all database directories and the reclaiming of unused space and returning it to the system. Because redistribution operations take considerable system resources, plan ahead when you want to add space to the database. For example
      extend dbspace e:\tsm_db\dbs7 on Windows
      extend dbspace /tsmdb/dbs7 on UNIX

The directories must be empty and accessible to the user ID of the database manager.

2) DSMSERV EXTEND DBSPACE, can be used to perform the same function as the EXTEND DBSPACE command, while the server is offline.

3) You should run the EXTEND DBSPACE commands while the server is not handling a heavy load.

4) You can also reduce or remove database directories if they are not required by using REMOVE DB command

Also Read: How to increase or decrease TSM DB, active log and archive log size ?

Increasing the TSM V7 Activelog size

If the log is running out of space, the current transaction is rolled back, and the server issues an error message and halts. You cannot restart the server until you increase the active log size. If you use the active log mirror, it will also increases to the new size. You can increase the size of the active log by completing the following steps
  • Issue the DSMSERV DISPLAY LOG offline utility to verify the size of the active log.
  • In the dsmserv.opt file, update the ACTIVELOGSIZE server option to the new maximum size of the active log. For example, to change the active log to 120 GB, enter the following server option: 
activelogsize 122880
  • If you want to use a new active log directory, update the directory name specified in the ACTIVELOGDIR server option.
  • The changes take effect when you restart the server.

TSM Server options to monitor Database and Recovery log

1) You can use server options to control some aspects of database processing. They are available during and after installation. The following database options are specified in the server options file during installation:
  • ACTIVELOGDIR
  • ACTIVELOGSIZE
  • ARCHLOGDIR
  • ARCHFAILLOGDIR
  • MIRRORLOGDIR
  • DBMEMPERCENT
2) The ACTIVELOGDIR, ACTIVELOGSIZE, ARCHLOGDIR, ARCHFAILLOGDIR, and MIRRORLOGDIR options control the location and size of the logs and mirrors. These options are set during initial configuration. 

3) DBMEMPERCENT is the percentage of system memory that is dedicated to the database. If DBMEMPERCENT is not specified, the default is applied, which is 70% - 80%.

4) You can use server options to control how Tivoli Storage Manager groups and transfers data. Several of these options pertain to the size of the transaction and you can use them for improving performance. Group options include the following items.
  • MOVEBATCHSIZE: Specifies the number of files to move and group in a batch, within a transaction (Default is 1000 files).
  • MOVESIZETHRESH: Specifies the threshold for the amount of data to move as a batch, within the same server transaction (Default size is 4096 MB).
  • TXNGROUPMAX: Specifies the number of files to transfer as a group between a client and the server between transaction commit points (Default is 4096 objects.)
Also Read: Take TSM DB backup immediately if you notice these messages






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