Selecting the type of connection to use when overriding parameters

When connection parameters are overridden at run time, ZIETrans uses the overrides to create a transformation connection that differs from the one defined when the application was created. The choice of which connection ZIETrans uses as a template for creating this new transformation connection is based on whether you specify the connectionName connection parameter:

If you do not specify the connectionName parameter, ZIETrans creates a basic transformation connection based on the ZIETrans application's default connection.
If you specify the connectionName parameter, but the value is not a valid connection name, ZIETrans creates a basic transformation connection based on the ZIETrans application's default connection.
If you specify the name of a background connection as the value of the connectionName parameter, ZIETrans creates a complete transformation connection based on the named background connection.
If you specify the name of the ZIETrans application's default connection as the value of the connectionName parameter (usually main), ZIETrans creates a complete transformation connection based on the ZIETrans application's default connection.

When ZIETrans creates a basic transformation connection, certain functions are disabled even if they were enabled for the connection chosen as the template connection. With the basic connection, pooling is always disabled, and the connect and disconnect time-outs are ignored, as are the connect and disconnect macros. The HOD connection parameters for the template connection, such as the host name, and port are copied from the template connection, and then any supplied connection parameter overrides are applied to create the new basic transformation connection. Notice that basic connections are always based on the application's default transformation connection.

When ZIETrans creates a complete transformation connection, all connection settings associated with the connection named by the connectionName parameter are used, including pooling settings, connect and disconnect macros, and connect and disconnect time-outs. Your connection parameter overrides, if any, are then applied to create the pool specification used to create the new transformation connection.

If you specify the name of a background connection as the value of the connectionName parameter, and specify no other overrides, you effectively switch which connection will be used as the transformation connection for that application instance.

All ZIETrans connections are based on a pool specification. A pool specification is an internal object that describes the properties of all connections created from it. The ZIETrans toolkit actually creates pool specifications, and the runtime uses these connection files, like main.hco, to create actual Telnet connections at run time. When you specify connection parameter overrides, the ZIETrans runtime will dynamically create a new pool specification object, if needed, to describe the properties of the new connection. Pool specifications are visible in the ZIETrans administration panel for Web applications. Pool specifications dynamically created when parameter overrides are specified, regardless of whether the connectionName parameter is specified, are automatically destroyed when the last active connection is terminated, provided that pooling is not enabled.

Connection parameter overrides can be different for each user accessing a ZIETrans application. For example, if each user specifies a different LUName override, ZIETrans runtime creates a different pool specification for each user. Ensure that pooling is disabled for the original connection so the pool specification is automatically destroyed. If multiple users specify exactly the same overrides, only one pool specification will be created, and reused to create many identically-configured Telnet connections. For example, if an entire department of users specifies a particular host name override, only one new pool specification will be created and destroyed when no more connections are using that specification.

To be able to specify the connectionName parameter as a connection parameter override, the parameter must be enabled for overrides on the Connection Parameter Overrides page on the Other tab in the project settings editor.