Upon startup, the PMDF Job Controller reads a configuration file which specifies parameters, queues, and channel processing information. This configuration information is specified in the file job_controller.cnf in the PMDF table directory, i.e., in /pmdf/table/job_controller.cnf (UNIX) or C:\pmdf\table\job_controller.cnf (NT). The format of the configuration file is described in Section 10.3.

If you want to modify the parameters associated with the default queue configuration or add additional queues, you can do so by editing the job_controller.cnf file, and then stopping and restarting the Job Controller with the UNIX command:

# pmdf restart job_controller

or the NT command

c:\> pmdf restart job_controller

On NT you can alternatively stop and restart the Job Controller from the Services screen under the Control Panel.

A new Job Controller process will be created, using the new configuration, and will receive subsequent requests. The old Job Controller process will continue to execute any requests it has queued until they are all finished, at which time it will exit.

Note that you can stop the Job Controller at any time using the UNIX command

# pmdf shutdown job_controller

or the NT command

C:\> pmdf shutdown job_controller

which will gracefully shut down, allowing any queued requests to finish. On NT you can alternatively shut down the Job Controller from the Services screen under the Control Panel.

The queue named DEFAULT in the Job Controller configuration file, by default the only queue, will be used for any requests which do not specify the name of a queue. PMDF channels defined in the PMDF configuration file¹ can have their processing requests directed to a specified queue by using the queue channel keyword followed by the name of the queue. This name must match the name of a queue in the Job Controller configuration. If the Job Controller does not recognize the requested queue name, the request will be ignored.

Typically, you would add additional queues to the Job Controller configuration if you wanted to separate processing of some channels from that of other channels. For example, you might need to prevent messages sent to a relatively slow channel from blocking processing of messages sent to other channels.

You might also choose to use queues with different characteristics. For example, you might need to control the number of simultaneous requests that some channels are allowed to process. You can do this by creating a new queue with the desired job limit and then use the queue channel keyword to direct those channels to the new, more appropriate queue.

In addition to the definition of queues, the Job Controller configuration file also contains a table of PMDF channels and the commands that the Job Controller is to use to process requests for each channel. There are two types of requests, termed "master" and "slave". Typically, a channel master program is invoked when there is a message stored in a PMDF message queue for the channel. The master program dequeues the message and delivers it. A slave program is invoked to poll a channel and pick up any messages inbound on that channel. While nearly all PMDF channels have a master program, many do not need a slave program. For example, a channel which handles SMTP over TCP/IP doesn't use a slave program because a network service, the SMTP server, receives incoming SMTP messages upon request by any SMTP server. The SMTP channel's master program is PMDF's SMTP client.