In the event of a SQL Server failure, automatic failover to the secondary SQL Server is possible if a witness has been deployed. However, if no witness has been configured, manual steps must be taken. Follow these steps to initiate a SQL mirror failover to a secondary server:
1. Before initiating the failover, confirm which server is acting as the Primary and which is acting as the Secondary by running the following command in Lync Management Shell:
Get-CSDatabaseMirrorState -PoolFQDN <Pool FQDN with failed SQL Server> -DatabaseType User
2. The command executed above will return a Principal and a Mirror value. To perform the failover, run the following command to fail over to the mirror ...