systems

Online COM versus offline An online COM system is used in an IBM installation by PAUL RICHMOND

F or at least a decade COM has been promising to replace paper as the primary output medium

for batch computer systems. Yet, so far, this promise has not been fulfilled. Paper continues to dominate, as more online systems introduce more batch reports including audit trials and printed copies of the database (just in case the online system is unobtain- able). All this means that computer installations contine to install more printers, storage becomes an even bigger problem and costs continue to rise. And all these additional printers are online to the host computer system.

The situation regarding COM recor lers is somewhat different. Despite the fact that online devices

Abstract: An advantage of COM is the avoid- ance of many of the problems involved in printing and storing large reports. There must be very few installations which use ofline printers and yet the vast majority of COM devices are offline. However online COM is available, it works, and in many cases is far cheaper than equivalent printers.

Keywords: data processing, computer output on microfilm, printers.

Paul Richmond is technical support manager for Cummins Engine Company Ltd.

have been available for at least the last decade, the vast majority of installed COM recorders are offline. In many cases this is easily explained, as most online devices are only available to the IBM user. Also COM bureau services are probably best handled ofIke, avoiding the overheads involved in converting, on a host computer, the tapes received from a range of computers. Indeed some COM bureaux do not even have a computer system to which a COM recorder could be attached.

Cost/performance figures

Before discussing the relative merits of online and oflline recorders, it is as well to consider the following cost/perform- ance figures so that they can be put into perspective with printers. A typical dumb recorder costs around L40 000, with more sophisticated recorders capable of formatting 270 pages in 1 ‘/z mins costing between E46 000 and E70 000. Compare this with 1 200 lines/min at a cost of E24 000 for the IBM 3203 printer or 15 000 lines/min at a cost ofE230 000 for the IBM 3800 laser minter.

For the IBM user comtemplating the installation of an inhouse COM recorcler there is a real choice to be made between online and offline

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devices. Some COM recorders (so called ‘dumb recorders’) require the data to be presented preformatted with the application program having performed all titling, indexing and formatting. More sophisticated recorders take normal print records and perform data extraction as necessary to control titling, indexing and formatting. The definition of this data extraction process is either a manual process or can be automated by preceding the print data with appropriate control records.

One of the big advantages of choosing an online COM recorder is the lack of operator action which is required when using such a device. The COM unit is directly attached to a channel on the host computer system and is usually configured to emulate a standard printer. Such data can be transmitted to it either through a driver program supplied by the COM manufacturer or by using a standard IBM JES writer. In either case the data is normally held on the system output queue. The formatting parameters necessary to produce titling, indexing etc. can be transmitted immediately preceding the data, or can be held on the COM recorder (on say a floppy disc) and a control command sent to cause these setup parameters to be loaded automatically. To produce a COM report the operator need only

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computer printout. (Not to scale)

activate the appropriate software and wait for the finished film or fiche to be produced.

For offline devices, a tape needs to be created on the computer system and transferred to the COM recorder. Depending on the sophistication of the recorder, the operator may have to enter several (or even many) commands into the COM recorder to cause the tape to be processed and the film or fiche produced. If the data on the tape has to be formatted the operator will have to check which formatting parameters are required and enter appropriate commands to cause these parameters to be loaded. All this can give rise to error.

With such high speed devices, large reports can be produced quickly, but should anything go wrong the same large reports can be lost or made unusable just as quickly. It is in this area that the case for offline COM recorders is probably strongest. As the input to these devices is via magnetic tape, whatever goes wrong in the production of the fiche or film, the tape still contains the original data and can

be reprocessed. Unless of course the tape itself is damaged.

Online COM recorders receive their data from the host computer through the data channel. Providing the COM recorder detects the error condition and sends appropriate error signals to the software running in the host computer, the output can be requeued to the system output queue and nothing is lost. However, if the COM recorder does not detect any error (say in the case of poor output film quality) then little can be done to retrieve the lost output short of rerunning the original application process. Of course the computer operator could instruct the software controlling the COM unit to hold duplicate output on the queue until the original output is verified as being acceptable, but this then means that operator intervention is greatly increased.

Case study

An example of the use of online COM is the system at Cummins Engine

data processing

systems

Company. The first online COM unit was installed in the Data Centre in 1973 and was a Datagraphix 4200 producing roll film which was developed offline in a separate depart- ment.

In 1981, the present online Datagraphix Auto COM II was installed, producing cut and processed master fiche. Where necesssary these are duplicated o0hne to produce the required number of copies, and the master copies are retained for periods depending on the requirements of the application. The COM unit is connected to a block multiplexor channel of the IBM 370/158 and emulates an IBM 32 11 printer.

The software used to transmit the output data from the system output queue to the COM unit is a standard JES writer, so that the operations group did not have to learn any new commands or procedures for pro- ducing COM output. The formatting parameters are created by a utility supplied by the manufacturer and required no changes to the application source codes. The generation and

transmission of these parameters may be handled in two ways. The first is to add an additional jobstep to the job creating the COM report, which creates an additional output dataset containing formatting parameters. When the JES writer processes the output for the job the formatting parameters are transmitted first, followed by the output data.

This process does have some limita- tions, especially when more than one COM report is produced within a single jobstep. As it is impossible to send more than one set of formatting parameters from the preceding jobstep, it is very diflicult to give each of the reports its own unique titling and indexing parameters. However, this process is used when testing the definition of the formatting para- meters.

Once the formatting parameters have been tested, they are transmitted to the COM unit, together with a control command which causes them to be stored on the system diskette of the COM unit with a name defined by the user. The output dataset for each

An online Datagraphix Auto COM installation, operating unattended.

COM report is then created, specifying an FCB (Forms Control Block) for the output dataset. The FCB is equivalent to the carriage control tape of older style printers, but for COM reports includes an extra field containing a load command instructing the COM unit to use a named set of formatting parameters from its system diskette. When the JES writer picks up the output dataset from the output queue, it first transmits the FCB to the COM unit, then loads the appropriate formatting parameters, and from then on the production of fiche is completely automatic. This approach is totally flexible, reports can each have different FCBs (and hence formatting parameters) or can use common or standard FCBs to give minimal formatting.

Cummins currently have in excess of 170 different FCBs defined for COM applications, generating more than 250 COM reports. The conversion of reports from paper to fiche requires no program changes, merely the creation of a set of formatting parameters and an FCB. This work is now undertaken by the data control department rather than programmers, and the popularity of fiche can be judged by the fact that approximately 70 reports have been converted as a result of user request. Prior ‘to the conversion from roll-film to fiche there had been no user initiated conversion for several years.

The view from the operations department is that at last COM is a true alternative to paper. To the operating system, and hence the operators, the COM unit is just another printer only requiring a single start command to initiate the production of fiche. In terms of direct operator intervention, the only action is to load new boxes of film, each box being the equivalent of over 100 000 sheets of paper. What could be easier?

q

Cummins Engine Company Ltd, Yarm Road, Darlin

$ on, County Durham DLl 4PW, UK

Tel: (0.25) 60606.

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