Online index rebuild corruption bug in SQL Server 2012 SP1

Online index rebuild corruption bug in SQL Server 2012 SP1

http://www.sqlskills.com/blogs/paul/online-index-rebuild-corruption-bug-sql-server-2012-sp1/

This is a quick blog post to let you know about a bug in SQL Server 2012 SP1 that can cause data loss when performing index maintenance.

The data loss issue can happen in some circumstances when you do a parallel online rebuild of a clustered index while there are concurrent data modifications happening on the table AND you also hit a deadlock and another error. Nasty when it occurs, but that should hopefully be a rare combination.

The workaround is to limit the online rebuild operation to be single threaded using the WITH (MAXDOP = 1) option.

There is a hotfix available – see KB 2969896 for more details. The fix is not listed as part of 2012 SP1 CU9 (see KB 2931078) or CU10 (see KB 2954099).

Update: there is now a fix available for 2012 SP2.