Digital Workshop

I have two Opus applications running at the same time One initiates the other. Both require to have access to a database. Which is the best approach??
To access the same database, same table?
To access same database different table
Or to access different Databases using different DSNs.
I have tried accessing the same database, same table. One application in a loop doing a database query every second, the other at random. I assume that sooner or later they will both try to access the database at exactly the same moment and cause an error??

Another question:-When doing a database query using access what is the best way of error trapping the event?? at the moment Access prevents duplicate Primary key entries, which is good, but it throws an error which kills the Opus program. The way I get round it at the moment is to check before doing any updates to see if the record already exists. Just wondered if there was a smarter way???

Thanks