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.
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.