11.1.1 About free pages

Before describing the pdreclaim command, this section describes pages and segments. Pages and segments can be in the statuses shown in the table below.

Table 11-1 Page and segment status

Page and segment statusDescription
Unused pageA page that has never been allocated.
Used free pageA page in which no data is stored because of data deletion.#1
Used pageA page that contains data as well as free area to which data can be added.
For a table that uses the free space reusage facility, this can include a page to which data cannot be added because it is not yet possible to use free area in the page resulting from data deletion.#1
Used full pageA page that stores data and has no free space to which data can be added.
For a table or index that does not use the free space reusage facility, this can include a page to which data cannot be added because it is not yet possible to use free area in the page resulting from data deletion.#1
Used segment#2A segment that contains table or index data. A segment that is filled with data and to which no more data can be added is called a full segment; any other segment is called a segment with available space.
Of the segments with available space, a segment whose pages are all empty because of data deletion (used free pages or unused pages) is called a used free segment.
Unused segmentA segment that has never been used. All tables (or indexes) in RDAREAs can use an unused segment.
Free segmentA segment that contains no data. Used free segments and unused segments are both free segments.
#1
Free area created by data deletion cannot be used until the transaction that performed the data deletion commits.
#2
A used segment is available only to the table or index whose data is currently stored in it. No other table or index can use such a segment.