Basically, the use of the WITH (NOLOCK) query hint performs a dirty read, of which I’m sure you can find oodles of examples on the Internet about. Microsoft introduced RCSI in SQL Server 2005 to help you reduce the amount of blocks, and with RCSI exclusively in use, database readers no longer block other readers or writers. I love enabling RCSI wherever appropriate, as long as the TempDB database is monitored to make sure that RCSI’s version store is not causing any issues (and it usually is just fine). It also goes without saying that with RCSI enabled, you should work to remove the WITH (NOLOCK) query hints from your code, as RCSI is superseded by NOLOCK and can still invoke dirty reads.
But… this Client is still seeing serializable connections that will occasionally cause issues. What else can we check?
Read on for a few tips.