DB2 UDB for z/OS Version 8 Performance Topics - IBM Redbooks

The Plug-In Options screen of Statistics Advisor is provided in Figure 3-57:
Figure 3-57 Statistics Advisor Plug-integrated with Visual Explain
Predefined defaults (you can add your own business specific defaults):
When Statistics Advisor observes a predicate using a default, SA recognizes that often
default values are skewed. So even if a column has high COLCARDF, if the SQL searches for
a ‘typical default’ (ACCT_NO = 0), then SA suggests collection of a single frequency on that
column. On the screen presented on Figure 3-58, you can define the collection parameters
for RUNSTATS, report type, collection type, check obsolete statistics dates, and enable
logging for Statistics Advisor. Logging means saving files with the name ssa.log, ssa.log.1,
ssa.log.2, and so on, and creates a trace.txt file, with the information you need to analyze VE
problems.
Figure 3-58 Predefined default values
Conflict thresholds tab:
We recognize that you run RUNSTATS with SHRLEVEL CHANGE on online systems. So it is
possible for table, index, and column statistics to be slightly inconsistent without causing
122 DB2 UDB for z/OS Version 8 Performance Topics