bauer, The exisiting DB2 table is not indexed by these columns, D_ACT & T_ACT. That's one of my concerns for performance issue. I will try CraigG's suggestion as well. Thanks.
danm, your query is much simpler than mine. Thanks to you and to all who provided solutions & suggestions.
I tested my own query afew times and it looks like it is working (not 100% sure) but you ...