As part of the Lync 2010 to Lync 2013 migration progress you have to migrate the CMS databases from Lync 2010 to Lync 2013 environment before the Lync 2010 environment can be decommissioned.
If you are using SQL Mirroring for your Back End databases you have to configure SQL Mirroring for the CMS databases manually.
Once the CMS is moved to the Lync 2013 environment you will notice the Databases are not automatically mirrored, the below PowerShell command can be used to configure SQL Mirroring for the CMS databases (XDS and LIS).
Install-CsMirrorDatabase –SqlServerFqdn “<SQL Server FQDN>” -DatabaseType “CentralMgmt” –Fileshare “<SQL Witness File Share>”
Check the databases again and you will see that they are now mirrored.