Administrator's Guide


Deleting Space from the Database or Recovery Log

You may want to delete database or recovery log volumes for a number of reasons:

When a database or recovery log volume is deleted, the server tries to move any data on the volume being deleted to the other physical volumes that make up the logical database or recovery log.

To delete space, perform the following steps:

  1. Determine if you can delete one or more volumes (page "Step 1: Determining If Volumes Can Be Deleted").

  2. As needed, reduce the capacity of the database to free up existing space in the database or recovery log, as described in "Step 2: Reducing the Capacity of the Database or Recovery Log".

  3. Delete the volume (page "Step 3: Deleting a Volume from the Database or Recovery Log").

Step 1: Determining If Volumes Can Be Deleted

To determine if volumes can be deleted from the database or recovery log, check the volume sizes and the amount of unused space.

To check the sizes of the volumes in the database, enter:

query dbvolume format=detailed

The server displays the following type of information:


+--------------------------------------------------------------------------------+
|Volume Name (Copy 1): VOL1                                                      |
|                                                                                |
|         Copy Status: Sync'd                                                    |
|Volume Name (Copy 2):                                                           |
|         Copy Status: Undefined                                                 |
|Volume Name (Copy 3):                                                           |
|         Copy Status: Undefined                                                 |
|Available Space (MB): 24                                                        |
|Allocated Space (MB): 24                                                        |
|     Free Space (MB): 0                                                         |
|                                                                                |
+--------------------------------------------------------------------------------+

In this example, you determine that VOL1, VOL2, VOL3, and VOL4 each have 24MB of available space, and VOL5 has 100MB.

To determine if there is enough unused space to delete one or more volumes, enter:

query db

The server displays the following type of report. Check the Maximum Reduction column for the amount of assigned capacity not being used.


+--------------------------------------------------------------------------------+
|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       176   4,096    50,176     4,755   9.5   9.5  |
+--------------------------------------------------------------------------------+

In this example, the database could be reduced by up to 176MB. This is enough space to allow the deletion of VOL1, VOL2, VOL3, and VOL4.

If there is not enough space on the remaining volumes, allocate more space and define an additional volume, as described in "Step 1: Allocating Space for the Database and Recovery Log" and "Step 2: Defining Database or Recovery Log Volumes to ADSM" and continue with "Step 2: Reducing the Capacity of the Database or Recovery Log".

Step 2: Reducing the Capacity of the Database or Recovery Log

The maximum reduction identifies by how much you can reduce the database or recovery log. By reducing the database or recovery log, you might be able to free up enough space to delete a volume.

You can reduce the capacity of the database or recovery log in 4MB increments. If you do not reduce in 4MB increments, ADSM rounds up to the next 4MB partition. Thus, if you specify 5MB, ADSM reduces the capacity by 8MB.

For example, assume that based on the utilization of the database, VOL5 alone could contain all the data. To reduce the database by the amount of available space in VOL1 through VOL4, 96MB, enter:

reduce db 96

Reducing capacity is run as a background process and can take a long time. You can issue a QUERY PROCESS command to check on the status of the process.

You can query the database to verify how much unused space is available after reduction. For example, after reducing the database by 96MB, the assigned capacity is 100MB and the maximum extension is 96MB, as shown in the following example:


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

Step 3: Deleting a Volume from the Database or Recovery Log

After you reduce the database or recovery log, use the smaller size for a few days. If the maximum utilization does not go over 70%, you can delete extra volumes.

Notes:

  1. You cannot delete volumes if there is not enough free space for the server to move existing data from the volume being deleted to other physical volumes in the database or recovery log.

  2. You cannot delete the last volume of the database or recovery log.

In our example, you determined that you can delete the four 24MB volumes from the database. You have reduced the database by 96MB. To delete VOL1 through VOL4 from the database, enter:

delete dbvolume vol1
delete dbvolume vol2
delete dbvolume vol3
delete dbvolume vol4

When you request that volumes be deleted from the database or recovery log, the server moves existing data from the volumes being deleted to available space on other volumes. Figure 50 shows data moved from VOL1, VOL2, VOL3, and VOL4 to available space on VOL5.

Figure 50. Deleting Database Volumes


Deleting Database Volumes


After the data has been moved, these volumes are deleted from the server.


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