Avoiding deadlock by using NOLOCK hint

Question

Once in a while I get following error in production enviornment which goes away on running the same stored procedure again.

Transaction (Process ID 86) wa

Answer 1

Occasional deadlocks on an RDBMS that locks like SQL Server/Sybase are expected.

You can code on the client to retry as recommended my MSDN "Handling Deadlocks". Basically, examine the SQLException and maybe a half second later, try again.

Otherwise, you should review your code so that all access to tables are in the same order. Or you can use SET DEADLOCK_PRIORITY to control who becomes a victim.

On MSDN for SQL Server there is "Minimizing Deadlocks" which starts

Although deadlocks cannot be completely avoided

This also mentions "Use a Lower Isolation Level" which I don't like (same as many SQL types here on SO) and is your question. Don't do it is the answer... :-)

• What can happen as a result of using (nolock) on every SELECT in SQL Server?
• https://dba.stackexchange.com/q/2684/630

Note: MVCC type RDBMS (Oracle, Postgres) don't have this problem. See http://en.wikipedia.org/wiki/ACID#Locking_vs_multiversioning but MVCC has other issues.