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Configuring database high availability using database mirroring

An architecture diagram showing database high availability                    using database mirroring
You can use database mirroring to provide high availability for the 
BlackBerry UEM
 database. Database mirroring is a 
Microsoft SQL Server
 feature that allows you to retain database service and data integrity if issues occur with the 
BlackBerry UEM
 database.
Microsoft plans to deprecate database mirroring in future versions of 
Microsoft SQL Server
, and recommends using the AlwaysOn feature for database high availability. Using AlwaysOn requires configuration steps before you install 
BlackBerry UEM
. For more information about using AlwaysOn, Configuring database high availability using Microsoft SQL Server AlwaysOn. The AlwaysOn feature cannot be used if you upgrade from 
BES5
 to 
BlackBerry UEM
 (the 
BES5
 database is upgraded to a 
BlackBerry UEM
 database). AlwaysOn is not supported for the components that manage 
BlackBerry
 OS devices.
When you configure database mirroring, you back up the principal 
BlackBerry UEM
 database (the database created during installation) and you use the backup files to create a mirror database on a different computer. You then configure a mirroring relationship between the two databases so that the mirror database performs the same actions and stores the same data.
To enable automatic failover, you set up a witness server to monitor the principal database. If the principal database stops responding, the witness starts an automatic failover to the mirror database. The 
BlackBerry UEM
 components connect to the mirror database and device service continues without interruption. A role switch occurs: the mirror database becomes the principal database, and the original principal database becomes the mirror database. This role switch can occur several times during a mirroring session.