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SNA NRJE User/Programmer Reference Manual: HP 3000 MPE/iX Computer Systems > Chapter 1 Introducing SNA NRJE
Introduction |
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Network Remote Job Entry (NRJE) is a data communications subsystem that provides HP-to-IBM batch communications in a Systems Network Architecture (SNA) environment. SNA is a comprehensive specification for distributed data processing networks, developed by IBM. SNA NRJE users at remote locations submit jobs to a host system for processing. The host sends output to SNA NRJE users at the remote location. SNA NRJE emulates a remote batch workstation as described below. SNA NRJE's relationship to the International Standards Organization (ISO) and SNA model communications networks is described in Table 1-1 “Relationship Between Network Models”, "Relationship Between Network Models." A computer network is designed in structured layers. The reason for a layered approach is to simplify the design of the overall network. Each layer rests on the next lower layer as a foundation. Each layer provides a service to the next higher layer in its own node, and relates to its counterpart layer on another node at a peer level. Direct communication with another node takes place only at the lowest layer of a network. Table 1-1 Relationship Between Network Models
A batch workstation is known to the host as a combination of one or more of the following peripheral devices, or their equivalents:
It is identified by RMTnnnn which represents the remote workstation number. Jobs are submitted from a remote workstation through card readers, or their equivalent, over a communication line to a host system. Output is received from a host system over a communication line to card punches and line printers, or their equivalent, at a remote workstation. An operator console at a workstation allows interaction with a host system by transmitting job entry subsystem commands and by receiving job entry subsystem messages. An operator console at a workstation cannot be used for an interactive session with a host system. Job entry subsystem commands can display information and can control the following:
A primitive workstation requires an operator. All jobs must be submitted by an operator, all output is received by an operator, and an operator executes all console commands and receives all console messages. Advanced workstations are designed to allow users other than the operator to perform the following tasks:
The user of an advanced workstation can work independently of the availability of the host system. Most actions relate to the domain of the workstation and do not enter into the host domain. An advanced workstation performs many functions without communicating with its host. NRJE on an HP 3000 emulates an advanced batch workstation. The SNA NRJE characteristics resemble an IBM 8100 Distributed Processing Program Executive (DPPX)/RJE workstation. An 8100 DPPX/RJE workstation is suitable for many distributed processing applications in many industries. It communicates with IBM System/370, 43xx, and 30xx, or plug-compatible processors using a 37x5 type communications controller. When DPPX is used with an SDLC communications link, the 8100 is operating in an SNA environment. In this case both a workstation console facility and multiple LU-LU sessions between an 8100 and a host system are supported. A DPPX/RJE operator controls each workstation. The operator can issue interactive DPPX commands to establish a communications link and to manage input/output sessions or devices. Also, the operator can enter host system commands and receive host system messages at the workstation console. The operating system also supports a Programmed Operator Facility, which allows user-written programs to carry out operator functions. DPPX allows a user to input jobs from a card reader, disk files, a diskette, or magnetic tape. A user issues a DPPX/RJE command to submit the name of the file to a transmission queue. The queue itself is a disk file containing the names of files with jobs. When appropriate operator commands are issued, DPPX/RJE transmits the files named in the transmission queue to the host system. A user can submit file names to a transmission queue even when an 8100 is not attached to a host. Job file names can remain in the queue until an operator sends the files to the host. When output returns to an 8100 over an SDLC link, DPPX/RJE handles the data set in one of two ways. The operator routes the data set either (1) directly to a printer or punch, or (2) to a disk for deferred printer or punch output. SNA NRJE workstations transmit jobs to the host via logical readers.You configure a virtual reader, which is an MPE spooled output device that holds submitted jobs until they are transmitted to the host. Workstations receive output data sets from the host via logical writers. NRJE assembles job input into a spool file. When communications with the host exist, job input spool files are transmitted to a host system as logical card reader data streams. Job output data is received from the host system in logical printer and punch data streams at the workstation and is then routed to the appropriate destination. The remote host console sends commands from the workstation to the host and receives console messages at the workstation from the host. An NRJE workstation communicates with a job entry subsystem at a host. The job entry subsystem is under the control of the host operating system. Several NRJE workstations can operate on an HP 3000. You must always identify which NRJE workstation you want to access. One spooled reader, a virtual reader, must be configured for each NRJE workstation. The spooled reader is used for queued transmission from an HP 3000 to the host system. A virtual reader on an HP 3000 has no corresponding definition at the host. NRJE users can submit jobs whether or not their HP 3000 is communicating with the host system. An NRJE user submits a job by designating a set of MPE files. A spool file is created and receives the MPE job input files in the order they are designated. Each spool file is an element in the workstation transmission queue. When communication with the host starts and the host system is accepting job input, each job is transmitted according to its position in the queue. If communication with the host system is not active, or if the host system is not accepting job input, the job remains in the transmission queue. Direct transmission of a job to the host--transmitting a job without first entering job input data into the transmission queue--is not supported. A workstation and host communicate with each other in an LU-LU session. In SNA, a workstation is a set of logical units (LUs). The job entry subsystem at the host is also an LU. In an LU-LU session between a workstation and a host, NRJE retrieves job input data, translates and compresses it when requested, prefixes SNA format headers, and passes it to the SNA link product on the HP 3000. The SNA link product transmits the data to the host. A spool file containing job input data is retained until it is successfully transmitted. Multiple data sets can be created for each job submitted to a host. An output data set is always created for each job submitted to a host for Job Control Language (JCL) logging. Data sets are received at an HP 3000 using an SNA link product. Data is decompressed and translated if desired. Data sets are returned to a logical output device, a logical writer, with those from a specific job typically making up one spool file. A logical writer must exist for each printer or punch defined at the host for your remote. NRJE uses the console command and message stream between a workstation and the host job entry subsystem. An NRJE user sends commands and receives messages through the console. All job entry subsystem commands configured for a workstation are permitted. (This, however, depends on the capabilities assigned the user by the node manager.) NRJE can be accessed two ways: interactively and programmatically. Interactive access is through the NRJE subsystem command interpreter. Programmatic access is through a user-written program calling NRJE intrinsics. Most NRJE commands correspond with intrinsics. These are the operating environments needed for SNA NRJE:
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