The 1970s

A typical IBM System/370 Model 135 system with reel-to-reel tape, card punch, CPU and disk drives, TP controller, printer, and card reader. Addition of a TP controller to the picture shows that by the early 1970s, communications was becoming an important part of S/370 systems.

IBM followed the success of S/360 by introducing System/370 in 1970. Virtual storage was added in 1972. Virtual storage expanded system capacity and made programming easier and more productive. Real memory options grew as monolithic memory technology replaced ferrite core. Real memory options for the S/370-135 ranged from 96 K to 256 K bytes. In disk storage, the IBM 3330 (100 MB per removable pack in early models) replaced older 2311 and 2314 technology.

After 27 releases, DOS/360 became DOS/VS. DOS/VS offered five partitions (later 7) and a relocating loader for effective multiprogramming. POWER (Priority Output Writers, Execution Processors, and Input Readers) was added for I/O spooling. One can only imagine how long it took to come up with that acronym. A new VSAM file system for balanced random and sequential processing became part of DOS/VS. Database/Data Communication (DBDC) became a fundamental part of VSE as the use of CICS grew. A hierarchical database known as DL/1 was available as well. At this time, DOS/VS became something we would clearly recognize today as a VSE system.

After a brief partial detour to the Netherlands, responsibility for the VSE system was consolidated at the IBM lab in Boeblingen, Germany.

A full eight drive IBM 3330 unit. Each disk contained 100 MB per removable pack. Operators were frequently called upon to mount and unmount packs.

In 1972, an imaginary DOS/VS customer might have a S/370-135system with 192K bytes main memory, 4-6 IBM 3330 disk drives, 4 IBM 3420 reel-to-reel tape drives, a 3505 card reader and 3525 card punch, a 3211 line printer, and maybe a TP controller.

Starting in the mid-1970s, some VSE customers introduced VM to supplement the capabilities of their basic VSE environment. With the introduction of the S/370-138, an update of the basic 135 design, IBM began to implement selected 'VM assists' in processor microcode. The assists were designed to reduce the 'overhead' of VM. The effect was startling. Once the performance of VSE under VM became 'acceptable', many VSE customers began to exploit VM. They added multiple VSE guests for more processing capacity than a single VSE guest, separated production and test guests to increase system integrity and improve staff productivity, and used CMS as their preferred interactive tool. In 2005, many VSE users continue to exploit the world-class virtualization technology of z/VM. In fact, the unsurpassed ability of z/VM V5 to run and manage multiple Linux guests adds new relevance to VM for many VSE customers.

In 1979, IBM introduced the IBM 4300 system with Large Scale Integration (LSI) logic and solid-state memory based on an advanced 64K bit chip. Real memory options ranged from 512K to 4,096K (4MB) bytes. Integrated adapters lowered overall hardware costs. Along with the 4300, IBM introduced new disk systems based on Fixed Block Architecture.

A typical IBM 4331 system with on-line data entry (beginning to replace punched cards), non-removable disk drives, and CPU.

DOS/VS became DOS/VSE. E stood for ‘extended’, or perhaps ‘e Series’ (the internal code name for the 4300). DOS/VSE offered up to 12 partitions. MSHP was added to enhance service and control of the system. ICCF became the interactive component. ICCF was based on ETSS, a ‘field developed’ program commonly used at the time. DOS/VSE also offered improvements such as ASI procedures, missing interrupt handler, DASD sharing, etc. ACF/VTAM became a component of VSE. A major extension was support for FBA disk devices. During this period, the practice of charging for IBM software became widespread.

In 1979, an imaginary DOS/VSE customer might have an IBM 4331system with 512K bytes main memory, 6 IBM 3310 (with 65 MB per drive) FBA disk drives (or perhaps a workhorse 3350 CKD disk system), 4 IBM 8890 reel-to-reel tape drives, a 3211 line printer, and a number of 3270 CRT terminals for data entry. Use of punched cards began to fade.



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