IBM 000-8697 User Manual

System Architecture

Within the extent, individual pages contain different types of data. Extent
pages can be separated into five categories:

■

Data pages

■

Index pages (root, branch, and leaf pages)

■

Bit-map pages (a 4-bit bit map if the table contains a

VARCHAR

,

BYTE

,

or

TEXT

data type or if the length of one row is greater than

BUFFSIZE

;

otherwise, a 2-bit bit map)

■

Blob pages

■

Free pages

Refer to

 for further information about the structure of a dbspace

data page. Refer to

for further information about the structure of

a dbspace index page. Refer to

 for further information about the

structure of a dbspace bit-map page. Refer to

mation about the structure of a dbspace blob page.

An extent might or might not include all five page types. Each page type
serves a different function within the extent.

Data pages contain the data rows for the table.

Index pages contain the index information for the table.

Bit-map pages contain control information that monitors the fullness of every
page in the extent.

Blob pages contain blobs that are stored with the data rows in the dbspace.
(Blobs that reside in a blobspace are stored in blobpages, a structure that is
completely different than the structure of a dbspace blob page. Refer to

 for further information about storing a blob in a blobspace

blobpage.)

Free pages are pages in the extent that are allocated for tblspace use but whose
function has not yet been defined. Free pages can be used to store any kind
of information: data, index, blob, or bit-map.

 illustrates the possible structure of a table with an initial extent

size of 8 pages and a next extent size of 16 pages.