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 status	Description
Unused page	A page that has never been allocated.
Used free page	A page in which no data is stored because of data deletion.#1
Used page	A 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 page	A 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#2	A segment containing 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; a segment whose pages are all empty because of data deletion (used free pages or unused pages) is called a used free segment.
Unused segment	A segment that has never been used. All tables (or indexes) in RDAREAs can use an unused segment.
Free segment	A 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.