This article was previously published under Q270126
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SQL Server 2000 only allows clustering of a single default instance per cluster. This means that when you upgrade a SQL Server 7.0 Active/Active cluster (two clustered default instances), you can only upgrade one of the instances in-place as a default instance. You must upgrade the other SQL Server 7.0 instance to a SQL Server 2000 named instance, by using the Copy Database Wizard.
SQL Server 2000 named instances listen on a dynamic port that is selected when the instance is first started. Existing pre-SQL Server 2000 clients are not able to connect to the named instance after the upgrade because the clients are expecting to be able to connect to a default instance that is listening on port 1433.
Client computers that do not have the SQL Server 2000 client utilities and/or Microsoft Data Access Components (MDAC) 2.6 are unaware of named instancing and therefore are only able to connect to the default instance. Hence, only a single virtual server is being used.
There are a few ways for clients to connect to both virtual servers. Because there should not be a problem connecting to the default instance of the SQL Server virtual server, this section focuses on what you can do with the second virtual server, the named instance.
Upgrade all client systems to instance compatible versions of MDAC. This should be MDAC version 2.6 or later.
Reconfigure the client to connect to the named instance.
Set up the non-default named instance to listen specifically on port 1433. By doing this the non-SQL Server 2000 compatible clients are able to successfully connect to the second virtual server. Also, the client computers are able to locate it on the same port on which the server was listening when the server was a SQL Server 7.0 server. You can do this by using the SQL Server 2000 Server Network Utility. Select Properties for the TCP/IP Enabled Protocol. Set this option on the server side. You might have to specify an alias on the client side to gain connectivity to this instance. You can do this from the Client Network Utility on the client side. Specify the alias to use TCP/IP and to dynamically determine the port, or manually specify the port number on which the instance of SQL Server is listening.
On all the clients set up an alias for the virtual server with the named instance, which allows all the non-instance-aware clients to connect over the alias. For more information about how to do this, click the following article number to view the article in the Microsoft Knowledge Base:
265808 How to connect to an SQL Server 2000 named instance with the previous version's client tools
For additional information about the topics covered in this article, see the following topics in Microsoft SQL Server 2000 Books Online:
Controlling Net-Libraries and Communications Addresses
Network Protocols for Named Instances
How to Upgrade from an active/active SQL Server 7.0 Failover Cluster