IBM 000-8697 User Manual

System Architecture

In every chunk, the page that follows the last Preserved page is the first of one
or more chunk free-list pages that tracks available space in the chunk. A
chunk free-list page contains the starting page (page offset into the chunk) of
each section of free space and the length of the free space measured in
number of pages.

Initially, the chunk free-list page has a single entry. For example, in any
dbspace initial chunk other than root, the starting page number of free space
is three. The reserved pages fill the first two pages and the chunk free list fills
the third. The length of the free space in the first entry is the size of the chunk,
minus three pages.

When chunk pages are allocated, the loss of free space is recorded by
changing the starting page offset and the length of the unused space.

When chunk pages are freed (for example, if a table is dropped), entries are
added that describe the starting page and length of each section of newly
freed, contiguous space.

Timestamp archive

Timestamp for this archive (decimal)

Logical log unique ID

ID number of the logical log file containing the
record of this archive

Logical log position

Physical location of this checkpoint record in the
logical log file

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Reserved pages

Chunk free-list page

Free pages