Printer back end, printer/plotter devices, and Qdaemon background process concepts

Print | concept | background | The backend of a process printer is a collection of programs that are called by the Qdaemon process of a spool program to manage print jobs waiting to be printed in the queue.

The back end of the printer performs the following functions:
Receive one or more lists of files to print from the Qdaemon process
Converts a property value using the Printer property value and format in the database that has been entered from the command line
Initialize a printer before printing a file
If necessary, run the filter to change the print data flow to the format supported by the printer
Provides filters for converting ASCII document formats only
Provides support for printing native language characters
Pass filtered print data to the printer device driver
Generate title and end pages
Generate multiple Replicas
Report printer error conditions, including paper-missing errors and request intervention errors
Report the problem detected by the filter
Clear after the print job is canceled
Provides a print environment that system administrators can tailor to meet specific print requirements

The MKVIRPRT command defines a virtual printer for the back end of the printer. Create a custom set of properties by copying a predefined set of properties for a particular type of printer.
Custom properties can be listed with the LSVIRPRT command, and through the CHVIRPRT command, web-based System Manager (enter WSM, then select the device)
or Smit (change/Show print queue feature options) to make changes.
Whenever the MKVIRPRT or CHVIRPRT command is used, the utility (Piodigest command) is automatically run to construct the read and use
Property value and the memory image of the lookup table.

The Qdaemon command invokes the piobe command (print job manager) and passes the flag option and the name of one or more files that will be printed.
The only flag option that is not passed is the spool flag option that was dropped by the Enq command because the Qdaemon command has turned on the printer device.
and redirects the standard output to the printer. The state file provides communication between the Qdaemon and the backend.

If a title page is required, the Piobe command retrieves the header page pipeline that generates the banner page. The title page pipeline is passed to the shell. In the pipeline,
The standard output of the title page filter becomes the standard input for the format Converter filter. The Format converter filter processes the banner page and writes the results to standard output.
The standard output of the format Converter filter becomes the standard input of the device driver interface program, which writes the filtered title page to the printer device driver.

Printer/Plotter devices

Special files in the/dev directory for the device. This file may be used when redirecting (for example, cat filename >/dev/lp0).
Device driver settings can be displayed and changed through the web-based System Manager (Input WSM, then the device) or the Lsdev and Chdev commands.
Printer commands can access printer devices only if you create a print queue for the printer device, or if you configure the printer in/etc/qconfig on the back of the printer.

Qdaemon

Qdaemon is the process of running and controlling queues in the background. It is usually performed by the STARTSRC command at system startup.
Qdaemon tracks print requests in the/var/spool/lpd/qdir directory and ensures that the jobs are sent to the appropriate printer at the right time.
It also tracks the status of the printer and stores the printer using data for system accounting. This information is stored in the/var/spool/lpd/stat directory and can be passed through the
Lpstat and ENQ-A commands to access. If the Qdaemon is stopped, it must be restarted through the SRCMSTR process.

Note: Do not stop the SRCMSTR process; it controls other daemon running on the system.