NHibernate, Should i use ReadCommitted or ReadUncommited Transaction Isolation Level?

Question

In a large business, should i use ReadCommitted or ReadUncommited Transaction Isolation Level by default when using NHibernate ?

By using ReadCommitted isolation, i've been facing in some locking on SELECT (Query) statements that become slow.

Answer 1

Well, if you're using SqlServer and have problems with ReadCommitted timeouts/locks, this is easily explainable. You probably just have to run this:

ALTER DATABASE your_db SET SINGLE_USER WITH ROLLBACK IMMEDIATE ;
ALTER DATABASE your_db SET READ_COMMITTED_SNAPSHOT ON;
ALTER DATABASE your_db SET MULTI_USER;

try this and then retest your readcommitted approach. I would stick to it.

Answer 2

The core of the question:

Should i use ReadCommitted or ReadUncommited Transaction Isolation Level ?

Well, they can give different results. So you're actually asking:

Can I use use different result-sets when that is faster?

The answer depends on the application, only you can decide. But in general customers, especially large businesses, are not very tolerant to this.