INSERTING INTO A DATABASE TABLE CONCURRENTLY

Hello, Is it possible for more than one process to insert rows into a databse table at the same time? I have more than one "C" processes that want to insert rows into the same table concurrently. Some of them succeed but others fail with an error of 271 (ISAM error 154) which has to do with locking. I'm using Informix OnLine 7.23. Any idea ? Thanks, Caterina.

Vincent Birlouez wrote: > > Hello, > > Is it possible for more than one process to insert rows into a databse table > at the same time? > > I have more than one "C" processes that want to insert rows into the same > table concurrently. Some of them succeed but others fail with an error of > 271 (ISAM error 154) which has to do with locking. Well, -271 is Could not insert row and -154 is Lock timeout. It looks like your table is set up with page level locking and the multiple processes are holding the lock for a relatively long time before committing. You got a timeout error rather than a row lock error probably because you have SET LOCK MODE TO WAIT n seconds in your code but the wait period is not long enough. If the processes are interactive and you are FETCHING the row FOR UPDATE while a user modifies it this is a bad strategy for just this concurrency reason. Rather fetch it without lock and then re-fetch with lock and verify the record before updating it. Anyway, change the lock level for the table to row level: ALTER TABLE mytable LOCK MODE (row); This will improve concurrency and reduce lockout problems. Also in the apps increase the LOCK WAIT period. Art S. Kagel