DB2 Help

Read/Write Specifications -- Fields and controls

Questions for recommended settings

Answer these questions to get recommended extent and prefetch sizes in the Recommended settings group.

What will be the average size of a table in this table space?

Less than 400 KB
Recommends an extent size of 8 4KB pages
Between 400 KB and 2 MB
Recommends an extent size of 16 4KB pages
More than 2 MB
Recommends an extent size of 32 4KB pages

You can calculate the size of a table by multiplying the byte count of a single row by the number of rows in the table. A rough estimate is all you need.
The extent recommendation is based on the fact that smaller tables are more efficiently stored in smaller extent blocks.
How many containers in this table space are on separate physical drives?
Type a number in this field or use the arrows to spin to the number you want.
The number in this field multiplied by the extent size is the recommended prefetch size.
The prefetch recommendation is based on the fact that if you have containers on separate physical drives, the database can prefetch from all of those drives at the same time.

Recommended settings

These fields contain recommended settings based on the answers you specify in the Questions for recommended settings. You can also modify the Extent size and Prefetch size fields directly.

Extent size: Type a number in this field or use the up and down arrows to spin to the number you want.
Prefetch size: This box contains a list of numbers based on factors and multiples of the extent size. To change this field, click on the down arrow to display the list of valid prefetch sizes and select one.