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Migratingto System/38 Upgradeadvice for IBM minicomputerusers

by DAVID GREENBLATT

T

he IBM System38 is not just another computer system; it may well be IBM’s architectural choice for the next generation of computer systems. This hypothesis is supported by the advanced architecture of the System38 and by its many features which could easily be extended to make it even more powerful. There are many groups currently expressing interest in the System38. The scope of interested organizations includes System/34 and System/36 users, and a large number of sites that

Abstract: The IBM System/38 was first introduced in 1978, with the latestmodel released in 1985. It provides an upgrade path for System134136 users and is an alternative to the 4300. The computer has a mandatory database with data dictionary. It supports interactiveterminals and has complex securityfeatures. Key-words:data processing, computer systems,computer communications. David Greenblatt is president of DGC Incorporated, an IBM systems consulting education organization.

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0011-684X/86/060291-04$03.00

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1986 Butterworth

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were previously using non-IBM equipment. IBM System/34/36 users have long needed hardware that offers increased performance; the System38 offers these users additional performance and architectural features which will make it a viable piece of hardware for several years. IBM has already diminished the conversion procedures necessary to go from the System34136 to the System38 through the release of more advanced conversion aids. The groups looking at the System/ 38 include those who are considering a new computer system such as the IBM 4300 series. The System/38 can provide an alternative for those sites considering even the large IBM 4300. Regardless of the measurements used, the System38 (especially the Model 40) offers direct performance competition to these models. Additionally, the System138’s integrated features are superior to those of the IBM 4300. The relative complexity of the System/38 means that potential users (and even many current users) are still unfamiliar with its potential and capability. This paper will provide an introduction to some of the new features of the System/38.

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Database and query facility

History The IBM System!38 was aMou~ced in 1978. It was the culmination of several years of IBM research and development. Each System38 development group (database, security, etc.) was directed by a speciallychosen expert and each group published technical papers on its design innovations. Initial deliveries of the System/38 were delayed by performance problems until June 1980. By the end of 1982, IBM had delivered several thousand systems to a diverse group of users. In January 1983, delivery began of the System38 Model 7 field upgrade. The Model 7 offered a 50% performance improvement over earlier models and the support of up to four Mbyte of memory and several Gbyte of disc. Although the System38 Model 7 offered capacities far exceeding those offered for the Systemi 34136, its price was somewhat prohibitive. In January 1984, the System38 product line was reshaped, prices were lowered and a new model, the System/38 Model 6, was announced. The System/38 product line had three models, as shown in Table 1.

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In 1985, IBM announced the System/38 Model 18, 20, 40 and dropped the Model 8 in favour of the Model 18. Again prices were lowered. These products have expanded the System/38 product line to five models. Listed in Table 2 are these models and each model’s system characteristics. Software features The releases of the System38 operating system, Controi Program Facility (CPF), have provided major functional enhancements as well as performance improvements. Since the major system faults have been corrected, the majority of the future CPF releases will concentrate on feature enhancements. Besides having the standard features of other, traditional computer systems, the System138 has features that have not before been provided together on a singk system. This paper will concentrate on some of these features: l l l l l

database and query facilities, interactive workstation support, extensive security, development support, extendable architecture.

The most impressive feature of the System’38 is its mandatory database management system. System/38 users who do not wish to use the database can define files in a ‘primitive fashion’ to the darabase, but they cannot ignore it. The database itself has a relational or table-like appearance to the user. Files in the database are either ‘physical’ or ‘logical’. Physical files contain data and can consist of only one record format. A logical file, on the other hand, is an index to the records in one or more physical files, The usefulness of the database rests in its logical file capability. System/38 logical files have: their own record formats, * elaborate key structures with automatically maintained indexes, l the ability to select or omit records from physical files, * the ability to join up to 32 physical files (read only). l

On non-database systems, these features must be provided by extensive, redundant, bug-prone application coding. On the Systeml38, the logicals provide only the required data in the proper sequence that is required. The database has its own data dictionary (called a Field Reference File). The data dictionary allows the user to define an application’s data fields, attributes and editing criteria in a single place. The physical file can reference the dictionary by field name. By changing a field definition in the dictionary, the effect can be

data processing

systems ‘rippled’ throughout the system, without requiring the user to alter manually a single line of program code. Another database feature of the System38 allows the user to define a program work. field as being ‘like’ a second field. If this second field is defined in the dictionary, then the characteristics of the work field are also dependent on the dictionary. This capability enables the rippling effect to correct even work field characteristics. Together, the data dictionary and the ‘like’ feature allow data definitions to be independent of the applications programs. Physical and logical database files and reference,s to the files can be examined using System/38 commands which report on the existing interrelationships. These reports give the System38 operator and/or manager an up-to-date review of the ‘data environment’. The Query utility program is intended to provide non-DP personnel with a means for easy retrieval of data from the System/38. The data may be viewed at a workstation or printed. The current release of Query already includes generation of tables, calculation of subtotals, averages and counts, flexible headings and user-specified report layouts. CPF Release 5.0 has features which will increase the usefulness of Query significantly. The author is familiar with one large banking institution which has already had very impressive results with teaching Query to its non-DP staff. Proper usage of the System/38 database can greatly simplify the control and m~ntenance of large, application software systems. The Query utility can provide a straightforward and simple means for producing reports which previously would have required programmer involvement.

Interactive workstation support System38 interactive be shared by multiple

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out special program coding. On other computers, a shared program must keep track of the workstation with which it is currently communicating and the data which is associated with the other workstations. The System/ 38 has a sophisticated means of executing programs so that the same program code can be concurrently shared by multiple users. Data validation can be performed before the data is received by the program. When the user defines a screen layout, field editing criteria

may be established. An attempt to enter data which violates this criteria is recognized and rejected immediately. The application programmer can thus omit the editing and exception logic which would otherwise be required in coding. The operator or DP manager can control the workstation environment through the ‘work management’ facilities. The work management feature requires that every Systemi38 job must run in a defined ‘subsystem’. Proper definition of (an) interactive subsystem(s) will improve performance and will enable priority control and enforce security in the interactive environment. Securig

The installation of security on the System38 can be a cumbersome task, but the provided protection is significantly more comprehensive than that of any other commercial system. Apart from the traditional password system, the System38 has ‘object level’ security. This object security requires positive authority to be granted before a user can access any object (file, program, queue, etc.). The authority may be granted to an object for everyone (public authority) or explicitly for a specific user. The granted security is divided into ‘object rights’ (existence - create/delete the object, management move the object, and operational - only to operate upon the object) and ‘data rights’ (read, update, add and delete).

One major problem of the System/ 38 security feature is knowing the best way to apply it. It should be evident that assigning specific rights to every object for every user is a tedious task with much room for errors and omissions. There is a much simpler means which is based on the ‘adoption’ of security, but many System38 sites are not aware of the proper method to implement this approach. To simplify the task of implementing security, IBM announced the addition of the Group Profile capability in Release 6.0. Development support IBM has unofficially proclaimed the System/38 to be a ‘productivity’ machine. Indeed, the time to write and maintain new applications may be reduced by 30% to 40% through the programmer support features provided by the Systeml38. The programmer has to write significantly less code to produce an application on the System/38 because: input and output file layouts and data structures can be directly copied from the databases, interactive editing of input fields will be done automatically by the System38, sorting and selecting is carried out through logical files. The System/38 has a full-screen editor which simplifies the entry and maintenance of source code. The editor permits the programmer to view two source files (or a source file and a compiler error listing) simultaneously on the same screen. The editor also does syntax checking, and for Control Language programs, the editor will give prompts for the proper fields to be entered. As an aid in maintenance, the editor affixes the current date to every source line which is altered. RPG II has been modified for the System38. The new language, RPG

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III

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plus, structured programming operation codes, many basic enhancements long needed in RPG, integration with the new System 38 features through new commands for doing many of the CPF functions. The System38 development tools also include an interactive debugging feature. The debugging tool allows the programmer to specify statements as ‘breakpoints’. Whenever the program which is being debugged reaches a breakpoint, it will halt and allow the programmer to investigate and modify the program values and indicators. The program can then be restarted. The System38 has a valuable feature which makes it relatively simple to operate development and production environments concurrently. A program which must be modified can be moved by a supervisor (with proper object authority) between the two environments and without any manual alterations it will reference the proper ‘objects’ defined for the specific environment. This ensures that a programmer who is working on a program will not corrupt data during testing which belongs to the production environment. Although the System38 has extensive ‘productivity aids’, many users have become discouraged by the amount of time that it takes to master the basic System38 concepts. Until the learning curve is over, it is common for application development to take longer than it would on a traditional system. The System138 learning curve period can exceed six months.

Extendable architecture The System38 is designed to grow without impacting the existing user applications. This is achieved by insulating the user from the hardware;

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the user software communicates with an ‘intelligent’ operating system/ microcode combination. Since resource assignments are not done by the user, only CPF and microcode changes will be necessary as new and additional peripherals become available. The System/38 uses a method for compiling user programs which also ensures that there is room for improved performance. The System38 compilers (currently RPG III, COBOL and Control Language) convert the user program into a second program called a ‘template’. The instructions in the template contain references to the original program and are high level; each instruction is as powerful as an instruction in a traditional high-level programming language. The template for a Control Language program is so similar to the original source program that a command is already available for ‘recreating’ the source program from the template. Each of these template instructions are ‘resolved’ and executed by a series of microcode instructions. The template design’s advantages are: new compilers can be easily written since they only have to convert the source statements into a template. execution performance can be improved by finding a faster means of translating and executing the instructions in the template. program debugging is much simpler on the System38 because the original source statement numbers and data names are contained within the template and are available for abnormal termination dumps. The benefits of the template scheme are apparent when one contrasts the System38 compiler organization to traditional compiler architecture. Other compilers reduce the source program to machine language and

linked it to any subroutines which are called. This machine language ‘module’ is then executed. This organization means that the compilers must be complicated tools capable of reducing high-level languages to machine language. Also, performance on such systems can only be improved by faster execution of the machine language instructions while debugging must be done by reading dumps. In each respect, the System38 architecture is superior.

Integrated features Though many of the discussed features are available from various vendors for other systems, a complete software/hardware system supplied by one vendor assures that: the system will perform better because the features are built into the operating system/microcode and not superimposed over an operating system, there will be similar user interfaces to the features, the features will be able to interact with each other. Clearly, it is useful to have a database which interfaces with the workstation support and security software, etc, problems in the use of the utilities will be resolved faster because there is only one vendor, the features will cost less.

Conclusion The author feels that the System138 is the most revolutionary system to be offered in the mainframe marketplace in several years. The extensive IBM research and development has produced a machine with multiple features and growth potential. Although there are some minor problems with the System38 product line, DI’ managers and technical personnel should examine the IBM System38 closely for a potential role in their own organizations. q DGC Incorporated, 1450 Preston Forest Square, Dallas, TX 75230, USA.

data processing