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NOLOCK on everything? NOTHANKS!!

A fellow tweeter posted the question today on Twitter so I thought I would do a quick blurb about NOLOCK which might help serve as a reference point:

“So how do you convince a team of developers that putting NOLOCK on every single query isn’t a recommended practice?”

He’s probably facing the questions/comments like:

“All NOLOCK does is reads uncommitted rows”

“NOLOCK helps contention on tables that are being updated”

I started “googling” around a bit and found several great articles talking about this subject:

Dave Does Data – NOLOCK Hint and Other Poor Ideas

Dave also links to these articles as well:

SQLCAT – Previously Committed Rows Might Be Missed NOLOCK

Tony Rogerson – Consistency Problem with NOLOCK

Itzik Ben-Gan – Allocation Order Scans with NOLOCK

A great quote I found as well:

“NOLOCK is like a chainsaw, it’s very useful but also dangerous.  I don’t think I would put it on any list of standards or best practices if those recommendations would be forced on people who don’t understand what they’re doing.” – Scott

Hopefully these links will give enough information for our DBA friend looking to defend himself vs them nasty developer types 🙂 hehehe

A good rule of thumb (that I like to use anyways) for any index hint is:

Only use an index hint when you can PROVE that there is no other way to solve your problem.

Enjoy!!

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One Comment

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