5.6.3 Points to consider when determining the page size in data DB areas

This subsection explains the points to be considered when determining the page size in data DB areas.

You can use one of the following methods to specify the page size of a data DB area:

Specifying the page size in kilobytes for the -p option of the adbinitdbarea initialization option in the adbinit command
Specifying the page size in kilobytes for the -p option of the adbaddarea DB area addition and modification option in the adbmodarea command

Organization of this subsection

(1) Data DB area for storing tables

Consider the following points when determining the page size for a DB area in which tables are to be stored:

The page size must be large enough to store base rows. When storing multiple tables in a DB area, specify a page size that can store the longest base row in any of the tables. If the page size is not long enough to store base rows, an error occurs during table definition. For details about how to determine the length of base rows, see 5.8.2 Determining the number of pages for storing each type of row.
The maximum number of rows that can be stored in a page is 255. Therefore, if the size of the page is larger than the total length of the rows, excess space that cannot be used is allocated, reducing the data storage efficiency. For example, if the row length is 100 bytes, the maximum amount of data that can be stored in a single page is 25,500 bytes (that is, 100 bytes × 255 rows). In this case, if the page size is set to 32,768 bytes (32 kilobytes), an area of approximately 7,000 bytes (32,768 bytes - 25,500 bytes - management area byte count) cannot be used and is wasted.

For the page size, specify 8 or 16 kilobytes.

For the page size, specify 8 kilobytes.

For the page size, specify the maximum value, which is 32 kilobytes.