I have seen runstats active on dw database during etl jobs.  It is also plausible that the database itself is configured to evaluate runstats/reorg

db2 get db cfg for database XXXX

Part of that output is [ these are not default settings ]

Automatic maintenance                      (AUTO_MAINT) = ON
   Automatic database backup            (AUTO_DB_BACKUP) = OFF
   Automatic table maintenance          (AUTO_TBL_MAINT) = ON
     Automatic runstats                  (AUTO_RUNSTATS) = ON
       Real-time statistics            (AUTO_STMT_STATS) = OFF
       Statistical views              (AUTO_STATS_VIEWS) = OFF
       Automatic sampling                (AUTO_SAMPLING) = OFF
     Automatic reorganization               (AUTO_REORG) = ON

In addition there is the possibility of configuring these activities to be constrained to certain days/times, but if memory serves, the default is any day/any time.