This article was previously published under Q257434
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In ODBC, when you use multiple data source names (DSNs) to connect to the same SQL Server server (and you use the same server name), the most recent DSN's Network Library replaces the Network Libraries in other DSNs.
There is only one Network Library entry under each SQL Server server name in the following registry key:
When a new DSN is created for the same SQL Server server, the existing Network Library under this registry entry is replaced by the Network Library used in the new DSN.
Steps to Reproduce Behavior
Open Control Panel. In the Control Panel dialog box, double-click ODBC Data Sources.
Create a DSN named DSN01, which uses named pipes, to connect to a SQL Server server named TestServer.
Create a second DSN named DSN02, that uses TCP/IP to connect to the same SQL Server server (TestServer).
In the ODBC Data Source Administrator dialog box, select DSN01, and then click Configure.
In the Microsoft SQL Server DSN Configuration dialog box, click Next. Click Client Configuration. In the Add Network Library Configuration dialog box, note that the Network Library has changed TCP/IP.
To use a specific Network Library to connect to SQL Server, you can set up an alias by using the Client Network Utility.