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LongEx Mainframe Quarterly - November 2014

technical: Do You Still Need PSF?

From the 1980s AFP has been the backbone of mainframe printing. Known in the early days as Advanced Function Printing (AFP), it surprises many that AFP is very much alive and kicking today. And not just for legacy application. Now known as Advanced Function Presentation, AFP has been enhanced to allow colour, Unicode input, and images in more friendly formats such as PNG and JPEG.

An essential component for AFP on z/OS has always been IBMs Print Services Facility (PSF). And the chances are that you're still paying for PSF today. But today documents are more often viewed online than printed. So do you still need PSF?

What PSF Does

In a nutshell, PSF is a printer driver. It takes AFP input, and produces output for AFP printers. Let's look at this more closely.

AFP input doesn't really exist as such. AFP isn't just a set of standards or input criteria, but an overall architecture. So when we talk about AFP input, we're really talking about the application formats that AFP-supporting printers can accept. There are a couple:

  • MO:DCA-P (Mixed Object:Document Content Architecture-Presentation). Sometimes called the AFP Data Stream (AFPDS), this is the base format used to describe text and graphics on a page for AFP printers.
  • XML
  • Plain text

However this input isn't ready for printing. It needs to be converted, which we cover in a second. It is also enhanced, by combining it with special resources like:

  • Page definitions - page setup
  • Fonts - standardise fonts outside of applications
  • Overlays - Text and images that are put over of documents. This can be used for forms and company logos
  • Form definitions
  • Object containers - other objects that can be included such as colour management resources, JPEG images, encapsulated PostScript resources and PDF resource objects

PSF takes the inputs from JES spool, adds in the special resources, and creates data ready for AFP printers. This output data stream is known as IPDS (Intelligent Printer Data Stream). This is actually a two-way data stream, with PSF interrogating the printer as to its capabilities and status, as well as sending the document information. PSF can send this IPDS data via channels, SNA or TCP/IP.

But this isn't all that PSF does. It can also manage the printers where the IPDS data is sent.

Today, mainframe sites often prefer to print on LAN printers, or even avoid printing at all, and archive output for online viewing. This need has spawned many products to allow normal LAN printers to print IPDS data, and to archive IPDS output for online viewing.

Removing PSF

So to remove PSF, you have two options:

  • Eliminate IPDS
  • Replace PSF

Eliminate IPDS

Many printers and software accept IPDS input. Let's start with printers. Many printer manufacturers market IPDS compliant printers, or kits to allow printers to accept IPDS format. Similarly there are many software solutions to allow normal LAN printers to print IPDS data. Moving away from printing, there are also many software solutions to manage IPDS data: from storage and archival to conversion to formats such as PDF, and online viewing and distribution. However all these options need IPDS data - they need PSF, or something else that can produce IPDS.

Some software will accept AFP input rather than IPDS: removing the need for PSF. For example, IBMs Content Manager on Demand will accept AFP input, and can store AFP documents itself. MPI Techs AFP Conversion Module also accepts AFP input to create PDF documents. Solimar Systems SPDE/iCONVERT converts AFP to other non-IPDS formats.

So the bottom line is: eliminating printers and software requiring IPDS eliminates the need for PSF.

Replace PSF

Many sites cannot eliminate IPDS. They may have PSF printers that cannot be replaced, or critical software that relies on IPDS. In these cases a PSF replacement is required: software that can produce IPDS. Although not drop-in replacements for PSF, there are several products that may fit the bill. Examples include:

  • VPS/IPDS
  • Oce PRISMAproduction Host
  • ISIS Papyrus Host
  • Solimar AFPDS::IPDS Conversion Module
  • Macro 4 Columbus Z

So moving to these or similar options may be a way to retire PSF.

Conclusion

PSF continues to be necessary for many sites with AFP printing requirements. From PSF printers to hardware and software accepting IPDS, PSF continues to be an almost essential component. However many sites may now have little or no requirement for PSF, opening the door to its retirement.


David Stephens