Symptoms
Assume that you enable Multiple Active Result Sets (MARS) in Microsoft SQL Server 2014. When you load data into a clustered columnstore index by parallel trickle inserts from different SQL Server sessions, you receive the following error message:
Note
35377: When MARS is on, accessing clustered columnstore indexes is not allowed.
Resolution
After you apply this hotfix, when you access clustered columnstore indexes through a MARS connection, the error 35377 does not occur any longer. But it still occurs if the concurrent data retrieval and data modification occur in a single MARS session that does not support columnstore indexes in SQL Server 2014.
This issue was first fixed in the following cumulative update of SQL Server.
Cumulative Update 5 for SQL Server 2014 /en-us/help/3011055
About cumulative updates for SQL Server
Each new cumulative update for SQL Server contains all the hotfixes and all the security fixes that were included with the previous cumulative update. Check out the latest cumulative updates for SQL Server:
Status
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.