Re: How to prevent dead locks ???

Venky9970@aol.com wrote: : We are getting dead lock errors in our production system, I looked at : informix manual for any hints on preventing it. It was mentioned that : by using certain algorithms dead lock can be prevented. : Can anybody let me know how to prevent dead locks. Here is the postgresql(www.postgresql.org) man page, that I wrote: FETCH(SQL) PostgreSQL FETCH(SQL) NAME lock - exclusive lock a table SYNOPSIS lock [table] classname DESCRIPTION lock exclusive locks a table inside a transaction. The classic use for this is the case where you want to select some data, then update it inside a transaction. If you don't exclusive lock the table before the select, some other user may also read the selected data, and try and do their own update, causing a deadlock while you both wait for the other to release the select-induced shared lock so you can get an exclusive lock to do the update. Another example of deadlock is where one user locks one table, and another user locks a second table. While both keep their existing locks, the first user tries to lock the second user's table, and the second user tries to lock the first user's table. Both users deadlock waiting for the tables to become available. The only solution to this is for both users to lock tables in the same order, so user's lock aquisitions and requests to not form a dead- lock. EXAMPLES -- -- Proper locking to prevent deadlock -- begin work; lock table mytable; select * from mytable; update mytable set (x = 100); commit; SEE ALSO begin(l), commit(l), select(l). -- Bruce Momjian | http://www.op.net/~candle root@candle.pha.pa.us | (610) 853-3000 + If your life is a hard drive, | 830 Blythe Avenue + Christ can be your backup. | Drexel Hill, Pennsylvania 19026