Transactions & locking

Hello all, A relatively simple, yet undocumented, question: After "Begin Work", all rows touched will be locked. However, does this locking happen to all affected rows at the start, or as they are affected? The reason for asking comes from the desire to use "Set Lock Mode to Wait". We have MANY different input systems that access their related tables in different orders. Obviously this can lead to a dealocking problem if two processes are waiting for the other release a needed table. Example: Prog1 updates Tables A, B, and C. Prog2 updates Tables C, A, and B. Both Progs run "Set Lock Mode to Wait" right before "Begin Work" and then proceed with their updates. When Prog 2 gets to its second step, Prog1 already has a lock on the row it needs (this can happen easily with this system!), so it begins to wait. Prog1, meanwhile, continues on to update table B, but when it tries to update table C, it finds that Prog2 has locked it. So Prog1 begins to wait! DEADLOCK!!! If the "Begin Work" locks all associated rows at once, then the chances of both programs colliding like this is much smaller (although not non-existent). But that would mean Informix is running the transaction's logic twice (once to find the rows to lock, the second to actually process the info). This seems too inefficient for even Informix to allow. Any help is appreciated! Michael Hoffman mrh@panix.com