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3-78 IBM Informix OnLine Database Server Administrator’s Guide
Monitor Extents
If you prefer to use a tblspace number and page number, the tblspace number
is stored 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
You can calculate the page number from the hexadecimal value of the rowid
as follows:
■ The two 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 about tbcheck -pp syntax, refer to page 7-38. For
further information about tbcheck -pp output, refer to page 7-43.
Monitor Extents
Monitor extents to check for chunk fragmentation (tbcheck -pe) or to
determine disk usage by table. Temporary tables are not monitored. Refer to
page 2-114 for further information about OnLine extents.
From the command line, execute tbcheck -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 to page 7-44 for further information about the tbcheck -pt output.
Execute tbcheck -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.