I never get a duplicate ID, because I lock the system table record while I get the next one. Even in the event of an update failure to the system table, they will just get an error when adding the record with the duplicate ID. And then I have an update routine which determines the next ID for all the tables. So if they get an error that way, they will just have to run the update procedure..

I really worry you will get a duplicate key problem pretty regularly if you have many users doing the same thing, like adding transactions. Sure, a milisecond isn't long, but it's long enough.

Adam