Ok, thanks, BTW I run my application with 512MB RAM, could you suggest what -c settings should I use for this environment?

I thought the problem occurs because of the RAM setting on the database engine .. because this problem IS ONLY OCCURS WHEN THE TRAFFIC IS HIGH.

currently I am using only -c 8MB like below:

Dbeng7.exe -q -c8m

is there any formula for doing this?

Many thanks again in advance

Regards
Winanjaya