STATISTICS PROFILE FEEDBACK field (STATFDBK_PROFILE subsystem parameter)

The STATFDBK_PROFILE subsystem parameter specifies whether statistics recommendations identified during query optimization directly result in modifications to statistics profiles.

Acceptable values:	YES or NO
Default:	Yes
Data sharing scope:	Same setting recommended on all members
Update:	option 24 on panel DSNTIPO
DSNZP`xxx`:	DSN6SPRM.STATFDBK_PROFILE

YES

Db2 modifies or creates statistics profiles based on statistics recommendations during query optimization.

Whenever Db2 writes new statistics recommendations to the SYSIBM.SYSSTATFEEDBACK catalog table, it also updates existing statistics profiles based on the recommendations:

If no profile exists, Db2 creates new profiles for some recommendations. The new profiles collect existing statistics (similar to the result of RUNSTATS SET PROFILE FROM EXISTING STATS) plus statistics for new and existing uncollected statistics recommendations.
Existing profiles are modified depending on the type of statistics recommendation:

TYPE='T'

No profiles are changed, and no profiles are created for this recommendation type.

TYPE='I'

If the existing statistics profile does not include the index, the index is added with default collection. Any existing list of indexes without FREQVAL or HISTOGRAM specified is changed to INDEX(ALL).
No profiles are created for this recommendation type.

TYPE='C' with NUMCOLS = 1

If the existing profile does not include the column, the column is added.
No profiles are created for this recommendation type.

TYPE='C' with NUMCOLS > 1

If the existing statistics profile does not include the column group, the column group is added with COLGROUP syntax. KEYCARD recommendations add the corresponding index.
If no statistics profile exists for the table, a new profile that includes the column group and INDEX(ALL) is created.

TYPE='F' or 'H'

If the existing statistics profile does not include the frequency or histogram statistic, it is added. Db2 automatically determines the number columns to collect. Histogram statistics are added without a NUMQUANTILES specification. The frequency or histogram statistics are added in COLGROUP syntax. However, if the recommendation is for an index on expression, INDEX syntax is used instead.
In no statistics profile exists for the table, a new profile that collects the frequency or histogram statistics and INDEX(ALL) is created.
If Db2 detects certain statistics that provide no value for query optimization, such as certain multi-column frequency statistics, it modifies the profile to prevent the future collection of the useless statistics. Db2 also removes the statistics from the relevant catalog tables and issues a message to indicate the removal.
If CREATE INDEX statement is issued, Db2 adds the index to the existing statistics profile for the related table.

NO

Db2 does not modify statistics profiles based on statistics recommendations during query optimization. However, Db2 might still write the recommendations to the SYSIBM.SYSSTATFEEDBACK catalog table, depending on the value of subsystem parameter STATFDBK_SCOPE.