Specifications

3-3
Spooler Overview
Spooler Concepts
The following terms relate to the spooler overview.
Formatter Filters
A formatter filter is part of the pipeline created and executed by the default backend for local
printer queues, piobe. A formatter filter provides the capability of either formatting an input
file or passing it through unmodified, based on an input parameter. Even if the formatter
passes the input file unmodified, it still sends printer commands to initialize the printer
before the input file is printed and restores the printer to its original state after printing is
complete.
It is the formatter filter that has the capability of using a virtual printer’s colon file to perform
extensive manipulation of a spooler print job.
Local and Remote Spooler Queues and Spooler Devices
A queue is an ordered list of requests for a specific device. A device is something that can
handle requests one at a time, such as a printer. Each queue must be serviced by at least
one device; often it can be serviced by multiple devices.
Local and Remote Printers
A local printer is a real printer attached to a local host, for which there is a local queue. All
jobs submitted to this queue are processed and printed on the host on which the queue
exists. A remote printer is a real printer attached to a remote host. The queue for a remote
printer specifies a backend whose function is to send the spooled job from the local host
across the network to the remote host. All jobs submitted to this queue, on the local host,
are sent across the network to the remote host where they are processed and printed.
Printer Devices
A printer/plotter device is a special file in the /dev/directory for a real printer. This file can
be used by redirection (for example, cat FileName > /dev/lp0) or by user–written, compiled
programs. Settings for this device driver can be displayed and changed using the splp
command. Before any of the spooler commands can access a printer device, a print queue
must be created for the device.
qdaemon
The qdaemon is a process that runs in the background under the auspices of the srcmstr
process. When you turn your system on, the startsrc command starts the qdaemon. While
the qdaemon can be started by the startsrc command or stopped by the stopsrc
command, the qdaemon supports only signal communications and thus cannot be queried
by the lssrc command.
The qdaemon tracks both job requests and the resources necessary to complete the jobs,
where the resources may be a real printer, some other real device, or even a file. The
qdaemon maintains queues of outstanding requests and sends them to the proper device
at the proper time. The qdaemon also records printer usage data for system accounting
purposes. It is the qdaemon that sets the backend for a spooler queue into execution.
If the qdaemon is aborted, it will be restarted by srcmstr.
Note: Do not attempt to stop the srcmstr daemon; it controls other daemons running on
your system.