A SharePoint environment contains an instance of Microsoft SQL Server 2008 R2. You plan to migrate data from the existing database to a new instance of SQL Server 2012. You need to configure SQL…

Configuring a named instance on the new SQL Server does not redirect existing connections; SharePoint connection strings would need to be manually updated to reference the new instance name.

A SQL Server alias is a client-side configuration stored on each farm server that maps a logical name to an actual SQL Server host and instance. By pointing the existing alias to the new SQL Server 2012 instance, all SharePoint web applications and service applications continue connecting under the same name they already reference, eliminating the need to update any SharePoint configuration.

Database mirroring is a high-availability and redundancy feature, not a migration mechanism, and failover to the mirror would still require connection string changes if the principal server hostname changes.

A single-node SQL Server cluster uses a virtual network name that differs from the original standalone server name, which would still require SharePoint to be reconfigured to use the new cluster name.