Symptoms
Assume that you have defined sequence objects in Microsoft SQL Server 2012 or SQL Server 2014. When you execute sp_sequence_get_range system stored procedures and NEXT VALUE FOR function in parallel on the same sequence object (for example, in different concurrent connections or in multithreaded applications), duplicate sequence value is generated.
Cause
This issue occurs because of a race condition for sp_sequence_get_range system stored procedures and NEXT VALUE FOR function when they are executed in the same sequence object in parallel. Both of them read and write to the current value of the sequence generator. However, there is a lack of correct synchronization mechanism between them.
Resolution
Service pack information
To resolve this issue, obtain Service Pack 1 for SQL Server 2014.
For more information about SQL Server 2014 Service Pack 1 (SP1), see bugs that are fixed in SQL Server 2014 Service Pack 1 .
This issue was first fixed in the following cumulative update of SQL Server.
Cumulative Update 6 for SQL Server 2014 /en-us/help/3031047
Cumulative Update 4 for SQL Server 2012 SP2 /en-us/help/3007556
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.