Multiplexed Connection

Some applications connect multiple times to the same database server on behalf of one user. A multiplexed connection uses a single network connection between the database server and a client to handle multiple database connections from the client. Client applications can establish multiple connections to a database server to access more than one database on behalf of a single user. If the connections are not multiplexed, each database connection establishes a separate network connection to the database server. Each additional network connection consumes additional computer memory and CPU time, even for connections that are not active. Multiplexed connections enable the database server to create multiple database connections without consuming the additional computer resources that are required for additional network connections.

To configure the database server to support mulitplexed connections, you must include in the ONCONFIG file a special NETTYPE parameter that has a value of SQLMUX, as in the following example:

NETTYPE SQLMUX

To configure the automatic use of multiplexed connections by clients, the entry in the sqlhosts file that the client uses for the database server connection must specify the value of m=1 in the options field, as in the following example:

menlo ontlitcp valley jfk1 m=1

You do not need to make any changes to the sqlhosts file that the database server uses. The client program does not need to make any special SQL calls to enable connections multiplexing. Connection multiplexing is enabled automatically when the ONCONFIG file and the sqlhosts file are configured appropriately. For information on the NETTYPE configuration parameter, refer to the chapter on configuration parameters in the IBM Informix: Administrator's Reference. For more information on the sqlhosts file, refer to The sqlhosts File.

The following limitations apply to multiplexed connections:

• Multithreaded client connections are not supported.
• Shared-memory connections are not supported.
• The ESQL/C sqlbreak() function is not supported.
• You can activate database server support for multiplexed connections only when the database server starts.

If any of these conditions exist when an application attempts to establish a connection, the database server establishes a standard connection. The database server does not return an SQL error.