A communications job is a batch job that is started by a program start request from a remote system. Job processing involves a communication request and appropriate specifications.
For a communications batch job to run on an i5/OS™ system, a subsystem description containing a work entry for communications jobs must exist on the system. The communications work entry identifies to the subsystem the sources for the communications job it will process. The job processing begins when the subsystem receives a communications program start request from a remote system and an appropriate routing entry is found for the request.
Job routing of communications jobs is determined by the program start request that is received from the remote system. When a program start request is processed on the target system, a fixed-length data stream that is used as routing data is created. Position 25 of the routing data will always contain PGMEVOKE for communications requests. Subsystem routing entries that specify a compare value of PGMEVOKE in position 29 typically have *RTGDTA as the program name. This means that the program name specified in the routing data (from the remote system's program start request) is the program to run.
If a special processing environment is required for certain communications jobs, you can add an additional routing entry to the subsystem description, specifying a compare value whose starting position is 37. This compare value should contain the program name for the program start request. The routing entry must have a sequence number lower than the routing entry that uses PGMEVOKE as the compare value. This method allows certain communications jobs to run with a different class or pool specification.
The security on the i5/OS system controls who can use communications devices as well as who can access the commands uses with the associated device descriptions. You should consider additional security measures when writing and running application programs on both remote and target systems.
The job description used for communications jobs is specified on the Add Communications Entry (ADDCMNE) command. The user specified on this job description is ignored. The system gets the user name for communications jobs from the program start request. If the program start request does not specify a user name, the system uses the default user value from the communications entry. To ensure a greater degree of system security, include user information about the program start request rather than specifying a default user in the communications work entry.