I have a locking problem.

Or at least no idea.

There is a database that for now is filled via exclusive imports.

The normal forms write through CA to tables, checking a synthetic timestamp (bound to the machine this is, but it normaly run on a terminal server) and changed fields, sometimes writing to multiple tables through transactions (the CA's build in is a bit a risk on that). It depends on pickup tables etc set by former import. The checks are on forms or business level, depending on use and how old the form is. The data to check is preloaded, because for now it is static.
This works pretty well.

Now the customer likes to import the data in a non exclusive way.

It's clear that I have to rewrite my import.

But how do
I check data that I only read for changes, (but I can not read them on every update, that's to much data gathering on some)
lock the update if the lookups are changing by import


Any ideas are welcome.

Lutz