There are some resources on the web that suggest that allowing snapshot isolation (by using ALTER DATABASE and SET ALLOW_SNAPSHOT_ISOLATION ON), and turning READ_COMMITTED_SNAPSHOT to ON can help performance of SharePoint systems – but none as far as I could find from Microsoft and the SharePoint team – and certainly none from Project. We have seen bad behavior when this option is enabled and definitely no performance improvements. One symptom that might indicate this issue is the Manage Queue page may not load. It isn’t something that can happen by accident, as it requires two specific changes at the database level, but it could well have been changed with good intention – perhaps to avoid locking issues that may have been better prevented by other preventative measures, such as good database maintenance.
To check if you have these settings configured get your DBA to run DBCC useroptions against your PWA databases. The default value they should see at the foot of the list is isolation level = read committed.
If it says “read committed snapshot” that means ALLOW_SNAPSHOT_ISOLATION and READ_COMMITTED_SNAPSHOT have been set to ON.
With these options ON, SQL Server will keep additional copies (in tempdb) of the previous values of rows currently being updated. This means that those values can be read – perhaps avoiding locks – but at the cost of making and managing the extra copy. And avoiding the lock (dead or alive) may not be what the application developer ever expected to happen – so you really need to understand the application before turning these options on and hoping for the best. A couple of good resources if you want more background – the TechNet article at https://msdn.microsoft.com/en-us/library/tcbchxcb(v=vs.110).aspx covers snapshot isolation – and the video from SQL Certified Master, Kimberly Tripp, at https://technet.microsoft.com/en-us/sqlserver/gg545007.aspx is very well worth a viewing. (Kimberly does also take wonderful photos of eagles – but I’ll let you ‘Bing’ for those…).
While I am in SQL Server mode a couple more things worth bringing up:
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