My understanding is that online indexing acquires locks at the beginning (Preparation) and end (Final) phases. However, we see a lot of DML queries blocked during the Build phase.
A sampling of the queries being blocked show they have a few things in common - the Wait Type is PAGELATCH_UP, the Wait Resource references a PFS page, and the query uses locking hints (NOLOCK, ROWLOCK, etc). Could locking hints be interfering?
Can anyone shed some light here or point me in the right direction?
Let me add, the actual command was:
ALTER TABLE dbo.Whatever DROP CONSTRAINT [PK_Whatever] WITH (ONLINE=ON);
This was the clustered index and there were no nonclustered indexes.