Transport resource list major node

The transport resource list element is not a resource, but describes the connectivity characteristics of the multipath channel line that is used for the connection.

An MPC connection can be used for both SNA & TCP/IP application traffic. See z/OS Communications Server: IP Configuration Guide. Any user of the connection is referred to as an upper layer protocol (ULP).

For a connection between VTAM® and an adjacent APPN node, the TRLE operand on the PU definition statement in the local SNA major node that defines the adjacent APPN node identifies the TRLE definition statement VTAM uses to route data over the connection.

For a connection between VTAM and a port on an Open Systems Adapter through which native access to an ATM network is achieved, the PORT definition statement in the XCA major node that defines the port identifies the TRLE definition statement VTAM uses to route data over the connection. The determination of which TRLE definition statement is used is made by matching the port name specified on the PORTNAME operand on the PORT definition statement to the port name specified on the PORTNAME operand on a TRLE definition statement in the TRL major node.

For all MPC connections defined by way of a TRLE definition, the subchannel addresses for the MPC connection must be defined. For all connections except OSA-Express, each subchannel address is dedicated to one direction of flow, either read or write, and the addresses are defined on the READ and WRITE operands.

With MPC dynamics support, if at least one WRITE and one READ subchannel path is allocated successfully, an MPC connection is activated. Additional paths (defined but not ONLINE) in an MPC group can later be dynamically added to the active group using the MVS™ command VARY device ONLINE. For example, if there is a need for an increase in capacity to allow for extra traffic over a channel, additional paths can be added to the active group without disruption. Similarly, paths can be deleted from the active group when no longer needed using the MVS command VARY device OFFLINE. Deletion of the last active READ or WRITE device can be controlled (allowed or disallowed) by MPC dynamics. See WRITE for more information.

For OSA-Express, there are two types of subchannels. There are subchannels dedicated to control flows, and there are subchannels dedicated to data. Control flows include signalling flows to set up and terminate connections, and data identified by the ULP to be transmitted over control channels. Data is any data the ULP identifies as not control. Data subchannels can be used for sending and receiving data through the OSA-Express device, or for receiving trace data from the OSA-Express device. The control subchannels are defined on the READ and WRITE operands, and the data subchannels are specified on the DATAPATH operand. As with Open Systems Adapter ATM access, the PORTNAME operand on the TRLE definition statement is used by TCP/IP for TCP/IP to achieve connectivity through the OSA-Express device.

For detailed instructions on setting up an OSA-Express feature, see zEnterprise System and System z10 OSA-Express Customer's Guide and Reference.

See the z/OS Communications Server: SNA Network Implementation Guide for more information about MPC connections.