To NOLOCK or NOT to NOLOCK, that is the question

Question

This is really more of a discussion than a specific question about nolock.

I took over an app recently that almost every query (and there are lots of them) has the noloc

Answer 1

In a traditional normalized OLTP environment, NOLOCK is a code smell and almost certainly unnecessary in a properly designed system.

In a dimensional model, I used NOLOCK extensively to avoid locking very large fact and dimension tables which were being populated with later fact data (and dimensions may have been expiring). In the dimensional model, the facts either never change or never change after a certain point. Similarly, any dimension which is referenced will also be static, so for example, the NOLOCK will stop your long analysis operation on yesterday's data from blocking a dimension expiration during a data load for today's data.