3-78 IBM Informix OnLine Database Server Administrator’s Guide

Monitor Extents

Ifyou prefer to use a tblspace number and page number, the tblspace number
isstored as a decimal in the partnum column of the systables table. Use the
HEX function to obtain the value as a hexadecimal:
SELECT HEX(partnum) FROM systables
WHERE tabname = tablename
Youcan calculate the page number from the hexadecimal value of the rowid
as follows:
■Thetwo right-most digits of the hexadecimal rowid refer to the slot-
table entry number for this row.
■The remaining digits define the page number.
For further information abouttbcheck -pp syntax, refer to page 7-38. For
further information abouttbcheck -pp output, refer topage 7-43.
Monitor Extents
Monitor extents to check for chunk fragmentation (tbcheck -pe) or to
determinedisk usage by table. Temporary tables are not monitored. Refer to
page 2-114 for further information about OnLine extents.
From the command line, executetbcheck -pt with a database name or table
name parameter to obtain the following information for each table:
■Number of extents
■First extent size
■Next extent size
Refer topage 7-44 for further information about the tbcheck -ptoutput.
Executetbcheck -pe to obtain the physical layout of information in the
chunk.The chunk layout is sequential, and the number of pages dedicated to
each table is shown. The following information displays:
■Dbspace name, owner, and date created
■Usage of each chunk in the dbspace, by chunk number
If OnLine is unable to allocate an extent in a chunk despite an adequate
number of free pages, the chunk might be badly fragmented.