Hi,

>>I checked with the data session window and found that some tables are still in a session "unknown(2)", it's kinda trouble for me to find out where did the system put these tables in the unknown session <<

This is usually an indication that the form which opened these tables has not been unloaded - probably because of a dangling reference. If that's the case then, as a short term solution, you could explicitly close these tables in the relevant forms Destroy() which probably does fire but you really need to track down the cause of the problem.

Regards,
Viv