Symptoms
Assume that you use the AlwaysOn availability groups feature in Microsoft SQL Server 2012 or SQL Server 2014. When communication between the Windows Failover Cluster and one of the replicas fails, the replica is no longer visible in the availability group. Additionally, the database changes to the restoring state.After this situation occurs, you don't receive any information from the SQL Server error log to further troubleshoot the problem.
Resolution
The issue was first fixed in the following Service Packs for SQL Server.
For more information about SQL Server 2012 Service Pack 3 (SP3), see bugs that are fixed in SQL Server 2012 Service Pack 3.
Service Pack 2 for SQL Server for SQL Server 2014About Service packs for SQL ServerService packs are cumulative. Each new service pack contains all the fixes that are in previous service packs, together with any new fixes. Our recommendation is to apply the latest service pack and the latest cumulative update for that service pack. You do not have to install a previous service pack before you install the latest service pack. Use Table 1 in the following article for finding more information about the latest service pack and latest cumulative update.How to determine the version, edition and update level of SQL Server and its components
More Information
For more information about the dropped-replica issue, see Issue: Replica Unexpectedly Dropped in Availability Group.
Status
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
