Overview

The Network Print Facility lets you print data from your z/OS® system on remote printers accessible through IBM® IP Services. The Network Print Facility supports the printing of the following types of output:

JES2 output
JES3 output
VTAM® SNA character string (SCS) output over LU type 1 sessions
VTAM 3270 data stream output over LU type 3 and LU type 0 sessions

The Network Print Facility accomplishes this by transforming VTAM or JES output print data into a format that existing LPD functions can process.

The Network Print Facility lets you decide where and how output will be printed through the use of a routing file and options file. The where portion is defined by the routing file. The how portion is defined through LPR options in the options file and through other data in the routing file.

The Network Print Facility allows user exits for installation-defined routing decisions or data modifications. It also provides a queue manager program to control the initial sending of each print job, retries of failed print jobs, and deletion of print data sets after a user-specified retention time.

The Network Print Facility incorporates the following functions:

For communication with printers in the TCP/IP network, the Network Print Facility uses the protocol defined in Request for Comment (RFC) 1179 and amendments.
- The Line Printer Daemon (LPD) is the remote print server defined by this protocol. The LPD can have queueing capability, in which case it performs as a print spooling mechanism and a print driver.
  In this book, the term LPD refers to any print server which observes this protocol; it is not meant to imply any specific product implementation.
- The Line Printer Requestor (LPR) is the client defined by this protocol. LPR code within the Network Print Facility manages the communication between the MVS™ system and the LPD.
  The Network Print Facility supports the same options as TCP/IP's LPR command, including translation. For more detail, see the LPR options described in the z/OS Communications Server: IP User's Guide and Commands and the translation tables topic in z/OS Communications Server: IP Configuration Guide.
Two capture points allow the printing of data from either JES or VTAM:
- For JES, an FSS writer for which the network administrator must specify one or more output classes. Output queued under any of those specified classes is routed by JES to the NPF FSS writer, which then prepares it for transmission to the LPD server.
- For VTAM, a VTAM capture point application program, which does processing for one or more logical printers. Each logical printer emulates a real SNA-network printer, supporting SNA character string (SCS) data streams over an LU type-1 session or 3270 data streams over an LU type-3 or LU type-0 session. For more information about SCS and 3270 data streams, see SNA - Sessions Between Logical Units and the 3270 Information Display System Data Stream Programmer's Reference.
  An application with data to print (usually CICS® or IMS™) must first start a session with a logical printer in the NPF VTAM capture point application. When print data is received over that session, NPF then prepares it for transmission to the LPD server.
  
  On the session, the NPF logical printer always acts as the secondary LU (SLU), and the application sending the print data acts as the primary LU (PLU). In this book, the sender of the print data will often be referred to as the session partner LU.
A combination of internet name or IP address and printer name allow routing of print data within the TCP/IP network. Because this information is not provided by MVS applications that use JES or VTAM to print data, the Network Print Facility provides a routing mechanism. The routing mechanism uses a combination of files and optional user exits to derive the internet name or IP address and printer name from data provided by MVS.
The internet routings and print functions are determined in either of 2 ways or by a combination of the 2:
1. Routing and options files created by the network administrator.
  These files provide information for routing and printing based on the following subsystems:
  VTAM
  
  logical printer name
  
  JES
  
  Class, destination, and forms (JCL parameters CLASS, DEST, FORMS)
  
  This information is used to build the key used to access the routing file. (These keys are referred to as major and minor names. Definitions for these names are within the parameter descriptions in EZAPPFL TYPE=ROUTING.) The routing file in turn contains the key of a record in the options file. Between the 2 records, the system constructs a routing data area, which contains both routing information and printing options. This routing data area is used to determine the actual printer destination.
2. User exits
  The Network Print Facility provides for user-written exits that can either replace the functions of the routing and options files or augment the information found therein.
  - The optional general routing exit (user-supplied), invoked prior to the retrieval of the routing record from the routing file, can replace the routing file function by creating the routing data area, or it can alter the key used to access the routing file.
  - The optional specific routing exit (user-supplied), invoked after the retrieval of the routing record or the invocation of the general routing exit, can alter the routing data area, including the internet name or IP address and the printer name.
  - The optional input record exit (user-supplied), invoked as each print record is processed to modify the print data stream (its principal purpose), can also modify the routing data area based on information found within the print stream.
  Each user exit is described in Writing exit routines to tailor the Network Print Facility.
The Network Print Facility's file creation macro and an ISPF interface can be used to build the routing and options files. See Creating the Network Print Facility files and Maintaining the Network Print Facility files with ISPF for more detail.
For each individual print job, the Network Print Facility creates a sequential print data set and adds a corresponding record to its queue file. The queue file record keeps track of the print data set's name and status, along with the processing rules copied from the routing data area. The Network Print Facility's queue manager periodically scans the queue file and performs actions such as initial send attempts, retries, retention or deletion on files as required. The ISPF panel interface can be used to display or modify queue file record data.
The Network Print Facility normally uses multiple address spaces.
For each of the following types of applications within NPF, there can be 0, 1, or multiple instances of the application running at any given time, and each instance of the application is a separately started MVS job or procedure running in its own address space:
- The VTAM capture point application
- The FSS writer acting as the JES capture point
- The queue manager
In addition, a TSO/E user authorized to use the Network Print Facility ISPF interface will require his own address space.