Before describing the pdreclaim command, this section describes pages and segments. Pages and segments can be in the statuses shown in Table 11-1.

Table 11-1 Page and segment status

Page and segment status	Description
Used page	A page containing table or index data. A page that is filled with data and in which no more data can be stored is called a full page; a page that contains no data due to data deletion is called a used free page.
Unused page	A page that has never been used.
Free page	A page that contains no data. Used free pages and unused pages are both free pages.
Used segment*	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 due to 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 unused segments.
Free segment	A segment that contains no data. Used free segments and unused segments are both free segments.

^* 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.