2.4.5 DB area automatic extension

(1) Unit for DB area automatic extension

When a DB area is automatically extended, its capacity is extended by one segment at a time.

The following figure shows an example of DB area automatic extension.

Figure 2‒20: Example of DB area automatic extension

When a DB area file is configured using a regular file, automatic extensions will reduce the performance of update processing. Therefore, we recommend that you take one of the following steps, and based on the results, initialize the necessary amount of DB area during database initialization or DB area addition/expansion:

• Make an estimate of the amount of DB area that you will need.

• Execute the adbdbstatus command in a small-scale test environment to determine the size of the DB area.

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(2) Maximum value for DB area automatic extension

In DB area automatic extension, one segment of storage is added to the DB area every time a space shortage occurs, up to its maximum value.

You can determine the maximum value automatic extension for each DB area file by rounding up the file size that was specified during database initialization or DB area addition/expansion to the nearest multiple of 16 terabytes. The following figure shows an example of the maximum value for automatic extension.

Figure 2‒21: Example of the maximum value for DB area automatic extension

Explanation

When two DB areas are initialized to 20 terabytes each during database initialization or DB area addition/expansion, 32 terabytes becomes the maximum value for automatic extension for each DB area file. Therefore, the maximum value for the two DB areas combined is 64 terabytes.

For a work table DB area, the maximum value for work table DB area files is the upper limit for automatic extension. It is not the value obtained by rounding up the area initialized during database initialization in 16-terabyte units.

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