System Architecture 2-105
tblspace Tblspace
tblspace Tblspace Entries
Eachdata page in the tblspace tblspace describes one tblspace in the dbspace
andis considered one entry. Entries in the tblspace tblspace are added when
anew table is created. The first page in every tblspace tblspace is a bit map of
thepages in the tblspace tblspace. The second page is the first tblspace entry,
andit describes itself. The third page describes the first user-created table in
this dbspace. Each tblspace tblspace entry (page) includes the following
components:
Tblspace Number
Each tblspace that is described in the tblspace receives a tblspace number.
Thistblspace number is the same value that is stored as the partnum field in
thesystables system catalog table. It also appears in a tbstat -t listing.
The tblspace number (partnum) is stored as an integer (4 bytes). The
followingSQL query retrieves thepartnum for every table in the database
anddisplays it along with the table name and the hexadecimal representation
ofpartnum:
SELECT tabname, partnum, HEX(partnum) hex_tblspace_name FROM systables
Page header 24 bytes, standard page header information
Page-ending timestamp 4 bytes
Tblspace header 56 bytes, general tblspace information available
from atbcheck -pt display
Column information Each special column in the table is tracked with
an8-byte entry. (A special column is defined as a
VARCHAR,BYTE, orTEXT data type.)
Index information Eachindex onthe tableis trackedwith a16-byte
entry.
Index column information Each column component in each index key is
tracked with a 4-byte entry.
Extent information Each extent allocated to this tblspace is tracked
with an 8-byte entry.