80 DB2 UDB V8.2 on the Windows Environment
UPDATE PROFILE ONLY
Enables RUNSTATS to modify an existing statistics profile in the system
catalog tables without running the RUNSTATS command options of the
updated statistics profile.
The statistics profile is stored in a visible string format, which represents the
RUNSTATS command, in the STATISTICS_PROFILE column of the
SYSIBM.SYSTABLES system catalog table. This is the RUNSTATS command
with SET PROFILE option:
runstats on table <db2user.tablename tablesample bernoulli (20) set profile
Figure 3-15 shows the stored value in the STATISTICS_PROFILE column of the
SYSIBM.SYSTABLES table resulting from the command:
from sysibm.systables where name = 'EMPLOYEE' and creator = '<db2user>'
Figure 3-15 Stored RUNSTATS profile in SYSIBM.SYSTABLES
3.4.3 Automatic reorganization
Table reorganization is used to reclaim the fragmented spaces of a table and to
ensure optimal I/O and query performance. The table reorganization process can
consume resources and have an effect on performance. Determining the right
time to reorganize a table is not a easy task for DBAs.
Prior to V8.2, DB2 had in-place reorg for both table and index high-availability
features. The automatic table and indexing de-fragmentation and re-clustering
features introduced in V8.2 enable DBAs to manage table and index reorg
without manual intervention.
The automatic table maintenance objectives define the tables to be evaluated for
the need of reorganization. Periodically, DB2 determines reorg candidates by
evaluating the tables with fresh statistics or tables where an automatic reorg did
not complete previously. Figure 3-16 on page 81 shows when the table or index
reorg will take place after evaluation.