Thanks Torsten! SQL Server 2012 SP2 contains fixes to issues that have been reported internally and through the customer feedback platforms and Hotfix solutions provided in SQL Server 2012 Service Pack 1 up to and including Cumulative Update 9. More Details in SQL Server Release Services blog: http://blogs.msdn.com/b/sqlreleaseservices/archive/2014/06/10/sql-server-2012-service-pack-2-sp2-rtm-has-released.aspx

THX Christoph, In a nutshell - and highly recommended: If you had installed hotfix FIX: Data loss in clustered index occurs when you run online build index in SQL Server012 (http://support.microsoft.com/kb/2969896). Service Pack 2 will effectively remove all of the fixes you got from the hotfix! So take care!