Process Selection

IBM® Connect:Direct® uses the parallel sessions capability so that multiple Processes can execute simultaneously between any two IBM Connect:Direct nodes. Process selection for each parallel session is based on a class that the user specifies on a Process.

Note: Parallel sessions support requires you to specify PARSESS=YES in the VTAM application definition for both nodes. If two nodes have differing values for parallel sessions, transfers are limited by the maximum number of sessions in the ADJACENT.NODE definition on the node where the Process is submitted. For TCP/IP connections, IBM Connect:Direct manages the parallel sessions and provides multiple connections between the two TCP/IP partners.

You define the maximum number of sessions between two nodes in the network map. Because each session has a corresponding class value, the maximum number of sessions and maximum number of classes are equal. Selection of a Process for execution in a given node is based on Process priority (the PRTY parameter of the Process statement) within session class. User-specified class values allow a Process to execute on the session having the matching class value or on sessions with higher class values. The default class is the value specified in the IBM Connect:Direct network map.

When one Process completes, IBM Connect:Direct selects another Process (if any) to run on the available session. IBM Connect:Direct searches until it finds the first Process with a class eligible to execute on the available session.

A typical use for classes is to define critical Processes with low class values so that more sessions are available for their execution. You can specify higher class numbers for time-consuming Processes; this enables sessions with corresponding lower class numbers to become available more frequently.