I am trying to understand the new option COLGROUP in V8 Runstats.

We use the following syntax that collects stats on all columns and all indexes.
RUNSTATS TABLESPACE tsname
TABLE INDEX(ALL)
REPORT YES UPDATE ALL

Does the COLGROUP option collects any extra stats other than the one ran as above? What's the advantage of COLGROUP and when should be used?

Also, is there any disadvantage of using KEYCARD for index runstats? Is it always preferrable?

We are using DB2 V8 for z/OS. Some in compatibility mode and some are NFM.

I appreciate your comments!

With COLGROUP, you can tell the DB2 utility to collect statistics about correlations of the values in columns list the group. A regular RUNSTATS won't do that automatically.

The manual says: