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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 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. If you change the size of a volume, Tivoli Storage Manager may not initialize correctly, and data may be lost.

Note:
Significantly increasing the recovery log size could significantly increase the time required to restart the server, back up the database, and restore the database.

Automating the Increase of the Database or Recovery Log

You can automate the process of increasing the database and recovery log sizes. 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.

Note:
There is one time when the database or recovery log might exceed the maximum size specified: If the database or recovery log is less than the maximum size when expansion begins, it continues to the full expansion value. However, no further expansion will occur unless the space trigger is updated.
To add the new volumes to the /usr/lpp/adsmserv/bin/ directory, issue the following commands:
define spacetrigger db fullpct=85 spaceexpansion=25
expansionprefix=/usr/lpp/adsmserv/bin/ maximumsize=200000
 
define spacetrigger log fullpct=75 spaceexpansion=30
expansionprefix=/usr/lpp/adsmserv/bin/ maximumsize=50000

The server then monitors the database or recovery log and, if the utilization level is reached, does the following:

Notes:

  1. The maximum size of the recovery log is 13GB. The server will not automatically extend the recovery log beyond 12GB.

  2. An automatic expansion may exceed the specified database or recovery log maximum size but not the 13GB recovery log limit. However, after the maximum has been reached, no further automatic expansions will occur.

  3. A space trigger percentage may be exceeded between the monitoring of the database or recovery log and the time that a new volume is brought online.

  4. If the server creates a database or recovery log volume and the attempt to add it to the server fails, the volume is not deleted. After the problem is corrected, you can define it with the DEFINE DBVOLUME or DEFINE LOGVOLUME command.

  5. Automatic expansion will not occur during a database backup.

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

    Also, deleting database volumes and reducing the database does not activate the trigger. Therefore, the utilization percentage can exceed the set value before new volumes are online.

  7. Setting a maximum size does not mean that the database and recovery log will always be less than that value. The value is a threshold for expansion. The server does not automatically expand the database or recovery log if its size is greater than the maximum size. The server checks the size and allows expansion if the database or recovery log is less than the maximum size. The server only checks the size that results after expansion to ensure that maximum recovery log size is not exceeded.

Recovering When the Recovery Log Runs Out of Space

If the log mode is set to ROLLFORWARD 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. In some cases, the server halts itself.

To restart the server, first format a new volume (see Using the DSMFMT Command to Format Volumes). Then use the DSMSERV EXTEND LOG command to extend the size of the recovery log. For example, after formatting a 21MB volume named new.reclog, extend the recovery log by issuing the following command:

dsmserv extend log new.reclog 20

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

Manually Increasing the Database or Recovery Log

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

Step 1: Creating Database and Recovery Log Volumes
Step 2: Extending the Capacity of the Database or Recovery Log

Step 1: Creating Database and Recovery Log Volumes

You can allocate space and define a database or recovery log volume in a single operation. For example, to allocate a 100MB database volume named VOL5 in the /usr/lpp/adsmserv/bin directory and define the volume, enter:

define dbvolume /usr/lpp/adsmserv/bin/vol5 formatsize=100

The available space of the database increases to 196MB, but the assigned capacity remains at 96MB. For Tivoli Storage Manager to use the space, you must extend the capacity (see Step 2: Extending the Capacity of the Database or Recovery Log). To verify the change, query 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 56 illustrates these changes.

Figure 56. Adding Volumes Increases Available Space



Available Space

You can also query the database and recovery log volumes to display information about the physical volumes that make up the database and recovery log.

Notes:

  1. The maximum size of the recovery log is 13GB, and the maximum size of the database is 530GB. If you allocate a volume that would cause the recovery log or database to exceed these limits, the subsequent DEFINE DBVOLUME or DEFINE LOGVOLUME command for the volume will fail.

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

  3. 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 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.

  4. To protect database and recovery log volumes from media failure, use mirroring. See Mirroring the Database and Recovery Log for details.

Using the DSMFMT Command to Format Volumes

You can still use the DSMFMT utility to allocate a database or recovery log volume. You would then issue the DEFINE DBVOLUME or DEFINE LOGVOLUME command without the FORMATSIZE parameter, and extend the database or recovery log (see Step 2: Extending the Capacity of the Database or Recovery Log).

To allocate an additional 101MB to the database as volume VOL5, enter:

> dsmfmt -db vol5 101

Step 2: 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, the server rounds up to the next 4MB partition. For example, if you specify 1MB, the server 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 57.

Figure 57. 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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