>hello,
>I want to ask when is the suitable time to issue PACK for the non-stop Internet Applications?

The only time you can issue a PACK is when a datasession has opened the table EXCLUSIVE - IOW, everything else is barred from even reading from the table for the duration of the PACK. IOW, you can only issue a PACK if your session is the only one accessing the table, and the table was accessed EXCLSUIVE. If you did not USE ... EXCLSUIVE, even if you only have one session holding the USE, you cannot issue a PACK.