IBM 000-8697 User Manual

Operating OnLine

One solution to chunk fragmentation is to cluster the index of all tables in the
chunk using

the ALTER TABLE

 statement. Another solution is to unload and

load the tables in the chunk. (For further information about what to do if
fragmentation exists, refer to

 for further infor-

mation about the tbcheck -pe output.

Execute tbstat -t to obtain general information about the limited set of active
tblspaces. The tbstat -t output includes the tblspace number and the
following four fields:

If a specific operation needs more pages than are available (

npages

 minus

nused

), a new extent is needed. If there is enough space in this chunk, the

extent is allocated here. If not, OnLine looks in other chunks for the space. If
none of the chunks contain adequate contiguous space, OnLine uses the
largest block of contiguous space it can find in the dbspace. Refer to

for further information about the tbstat -t output.

Monitor the indexes to verify index integrity or to monitor the number or
contents of key values in a specific index.

Refer to

 for a detailed discussion of index page structure. This

background information is needed to interpret most of the tbcheck -pk, -pl,
-pK

, and -pL output.

When you check and print indexes with tbcheck, the uppercase options
include rowid checks as part of the integrity checking. The lowercase options
only verify the B+ tree structure. Refer to

 for further information

about using the tbcheck utility.

The tbcheck -pK or -pL options verify and repair indexes, check rowid
values, and display the index values. Either option performs an implicit
tbcheck -ci

 or -cI.

npages

are the pages allocated to the tblspace.

nused

are the pages used from this allocated pool.

nextns

is the number of extents used.

npdata

is the number of data pages used.