There are times when servers are physically removed from your farm environment before they are removed from the SharePoint farm instance.  When this happens, SharePoint can have orphaned data remaining in its database making it impossible to remove the server through Central Administration without some manual intervention.
Note:  It is important to remove these orphaned servers [...]

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To configure connection specific alias, to aid in the installation of databases driven products (such as SharePoint/WSS), you can configure clients connections through the SQL Server Client Network Utility located at C:\WINDOWS\system32\cliconfg.exe.

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