Administrator's Guide


Increasing the Size of the Database or Recovery Log

As your requirements change, you can increase or decrease the sizes of the database and recovery log. You can automate part of the process of increasing the sizes, or you can perform all the steps manually. See Automating the Increase of the Database or Recovery Log or Manually Increasing the Database or Recovery Log.

Attention: Do not change the size of an allocated database or recovery log volume after it has been defined to TSM. If you change the size of a volume, TSM may not initialize correctly, and data may be lost.

If the log mode is set to ROLL-FORWARD and either the recovery log is too small or the database backup trigger is set too high, the recovery log could run out of space before database operations complete. If this happens, you may need to stop the server without enough recovery log space to restart the server, or the server halts itself.

To restart the server, first format a new volume and then use the DSMSERV EXTEND LOG to extend the size of the recovery log. For example, after formatting a 21MB volume, extend the recovery log by issuing the following command:

dsmserv extend log dsmserv extend log new.reclog

After the server is running, you can do the following:

Automating the Increase of the Database or Recovery Log

TSM lets you automate the process of determining when the sizes of the database and recovery log must be increased. With a DEFINE SPACETRIGGER command, you can specify the following:

For example, assume that you have a 100GB database and a 3GB recovery log. You want to increase the database size by 25 percent when 85 percent is in use, but not to more than 200GB. You also want to increase the recovery log size by 30 percent when 75 percent is in use, but not to more than 5GB. Issue the following commands:

define spacetrigger db fullpct=85 spaceexpansion=25
 maximumsize=200000
 
define spacetrigger log fullpct=75 spaceexpansion=30
 maximumsize=50000

TSM then monitors the database or recovery log. If the utilization level is reached, TSM does the following:

You could set up a management application that would begin an automatic expansion when the message is received.

Notes:

  1. The maximum size of the recovery log is 5.5GB. If you allocate a volume that would cause the recovery log to exceed this size, the subsequent DEFINE LOGVOLUME command for the volume will fail.

  2. The database and recovery log utilization percentage may not always be below the space trigger value. TSM checks utilization after a database or recovery log commit.

Manually Increasing the Database or Recovery Log

To add space to the database or recovery log, do the following:

Step 1: Allocating Space for the Database and Recovery Log
Step 2: Defining Database or Recovery Log Volumes
Step 3: Extending the Capacity of the Database or Recovery Log

Step 1: Allocating Space for the Database and Recovery Log

To allocate database and recovery log volumes, use ANRFMT or ANRFMT2. If you have set the space trigger and received message ANR4413I or ANR4414I, use the value from the message.

The maximum size of the recovery log is 5.5GB, and the maximum size of the database is 500GB. If you allocate a volume that would cause the recovery log or database to exceed these sizes, the subsequent DEFINE DBVOLUME or DEFINE LOGVOLUME command for the volume fails.

Notes:

  1. For performance reasons, define more than one volume for the database and recovery log, and place these volumes on separate disks to allow simultaneous access to different parts of the database or recovery log.

  2. When possible, assign each database and recovery log volume to separate DASD strings, preferably on DASD with different control units and channels.

  3. To protect database and recovery log volumes from media failure, use the mirroring feature. See Mirroring the Database and Recovery Log for information on the mirroring feature.

  4. To use disk space efficiently, allocate a few large disk volumes rather than many small disk volumes. In this way, you avoid losing space to TSM overhead processing.

    If you already have a number of small volumes and want to consolidate the space into one large volume, see Decreasing the Size of the Database or Recovery Log.

Step 2: Defining Database or Recovery Log Volumes

To define a database volume named VOL5, enter:

define dbvolume vol5

When defined, the volume becomes a part of the logical view of the database. Thus, TSM sees a single logical database volume, which is now composed of five physical volumes. Because 1MB from VOL5 is used for overhead process, 100MB is added to the database to increase the available space to 196MB. However, the assigned capacity remains at 96MB, and TSM cannot use the space until the capacity is extended (see Step 3: Extending the Capacity of the Database or Recovery Log).

After you define your volumes, you can verify the change by querying the database or recovery log. For example, to query the database, enter:

query db

The server displays a report, like this:

+--------------------------------------------------------------------------------+
|Available Assigned   Maximum   Maximum    Page     Total      Used %Util  Max.  |
|    Space Capacity Extension Reduction    Size     Pages     Pages       %Util  |
|     (MB)     (MB)      (MB)      (MB) (bytes)                                  |
|--------- -------- --------- --------- ------- --------- --------- ----- -----  |
|      196       96       100        92   4,096    24,576        86   0.3   0.3  |
+--------------------------------------------------------------------------------+

The value in the Maximum Extension field should equal the available space of the new volume. In this example, a 101MB volume was allocated. This report shows that the available space has increased by 100MB; the assigned capacity is unchanged at 96MB; and the maximum extension is 100MB. Figure 57 illustrates these changes.

Figure 57. Adding Volumes Increases Available Space



Available Space


You can issue the QUERY DBVOLUME and QUERY LOGVOLUME commands to display information about the physical volumes that make up the database and recovery log.

Step 3: Extending the Capacity of the Database or Recovery Log

The database and recovery log are extended in 4MB increments. If you do not specify the extension in 4MB increments, TSM rounds up to the next 4MB partition. For example, if you specify 1MB, TSM extends the capacity by 4MB.

To increase the capacity of the database by 100MB, enter:

extend db 100

After the database has been extended, the available space and assigned capacity are both equal to 196MB, as shown in Figure 58.

Figure 58. Extending the Capacity of the Database



Database Capacity


You can query the database or recovery log (QUERY DB and QUERY LOG commands) to verify their assigned capacities. The server would display a report, like this:

+--------------------------------------------------------------------------------+
|Available Assigned   Maximum   Maximum    Page     Total      Used %Util  Max.  |
|    Space Capacity Extension Reduction    Size     Pages     Pages       %Util  |
|     (MB)     (MB)      (MB)      (MB) (bytes)                                  |
|--------- -------- --------- --------- ------- --------- --------- ----- -----  |
|      196      196         0       192   4,096    50,176       111   0.2   0.2  |
+--------------------------------------------------------------------------------+


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