Operating Systems

This golden age culminated when function-rich VM/SP Release 4 (see Figure 3) enabled VM to extend its reach through modern networks. Key components included the introduction of the Group Control System (GCS) and with it VTAM, VTAM SNA Console Support (VSCS), and management via NCCF/NetView or NetMaster. GCS was CMS Operating System (OS) simulation on steroids. Enough MVS system calls were implemented to enable VTAM to operate; for example, GCS provided true multi-tasking. VM systems programmers could now enjoy the wonders of VTAM configuration coding, NCP generation, and the almost mystical procedures of getting the Network Control Program Packet Switching Interface (NPSI) up to give the VM system access to X.25. A new version of the remarkable Remote Spooling Communications Subsystem (RSCS) was announced; it also took advantage of the new facilities.

Some of us thought GCS had far more potential than was ever realized. For example, at the TAB of New South Wales in Australia, some simple modifications enabled PL/I V2.3 to run, and by exploiting the GATE and DATE features of NPSI, a complex, powerful message switching system was created.

Later, VM/HPO 4.2 was a major highpoint for VM; it extended VM to the high-end, enabling large workloads to be consolidated and managed. VM now ran on the smallest of the 9370s to the largest of the 3090s.

Little known around this time, TCP/IP was now available as a product (5789-HAL), having emerged as WiscNet’s TCP/IP (see Figure 4) for VM/SP 2 and 3. Although popular with the academic users of VM, it’s doubtful anyone at the time saw the impact this piece of software would have in the future.

Storm Clouds Gather: The Late ’80s

Widespread introduction of the PC became a challenge. Suddenly, computing power was no longer confined to a data center. Expectations changed and established hierarchies were challenged. The move to “departmental processing” was on. This evolved into the semantically empty phrase “client/server,” a marketing term that was confused with IT architecture. Out of this, we saw the development of the 9370 series of hardware, which was aimed squarely at the VM and VSE base.

Another challenge was one of IBM’s own making. VM was labeled as “strategic.” This can be a good thing, but it also meant it was more visible within the organization. Les Comeau, in his 1982 presentation to SEAS, describes the advantages of flying under the radar when VM’s predecessor, CP-40, was first developed: “It would be extremely self-gratifying to attribute that success to brilliant design decisions early on in the program, but, upon reflection, the real element of success of this product was that it was not hampered by an abundance of resources, either manpower or computer power (see Les Comeau: “CP/40—The Origin of VM/370” at www.garlic.com/~lynn/cp40seas1982.txt).

The former advantages of low visibility and limited access to resources were now elusive. With lots of resources comes lots of attention.

Coincidentally or not, the policy of Object Code Only (OCO) was introduced. Ironically, this was the period when Linux made its debut. Much has been written about the OCO battles and there isn’t much more to add to the debate, except to note that there were decisions coming down from on high to a community that had worked differently and well for many years preceding the decision.

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