Collecting statistics for whole database (DB2)

REORGCHK UPDATE STATISTICS ON TABLE ALL
will end up collecting statistics on all tables.

or
REORGCHK UPDATE STATISTICS ON SCHEME DB2ADMIN
will do so for the said schema.

Statistics will be collected at the level of default RUNSTATS options.
Applies to DB2 LUW only. Here is the devworks article:
http://www.ibm.com/developerworks/data/library/techarticle/dm-0412pay/