Hi,
Thank you for your information.
I think the main mistake in my application is, I re-use the PK. I don't have any unique integer used as PK, instead i am using value such as user entered customer ID as PK. And my app allow the deleted PK value to be re-used. for example:

PK       Delete Mark
VIP01       .T.       && *****
VIP02       .F.
VIP01       .F.       && Reused

Therefore, it cause problem when comparing records between working and backup record. The record marked '*****' will be insertewd into my forward table either. Any ideas?

Thank you