14.2.2 Setting the percentage of free pages in a segment

The percentage of unused pages allocated in a segment when a table is defined is called the percentage of free pages in a segment. Free pages here refers to unused pages. The following figure provides an overview of the free pages in a segment.

Figure 14-2 Overview of percentage of free pages in a segment

[Figure]

Organization of this subsection
(1) Effects of specifying a percentage of free pages in a segment
(2) Criteria
(3) Specification
(4) Notes

(1) Effects of specifying a percentage of free pages in a segment

Improved performance:
When data is added to a table for which a cluster key is specified, the data is stored in a page close to the cluster key value, which means that the number of data input/output operations is reduced.

(2) Criteria

(3) Specification

To specify the percentage of free pages in a segment, use the PCTFREE operand of the CREATE TABLE definition SQL statement.

(4) Notes

If the percentage of free pages in a segment is set to 0 for a table for which a cluster key is specified, it will not be possible to store added data close to the cluster key values. As a result, the data storage condition becomes poor and reduction in the number of data input/output operations can no longer be expected.