VAX VMS

The OpenVMS (Virtual Memory System) operating system (OS) is a multi-user, multiprocessing OS that was designed by Digital (now owned by Hewlett-Packard) for use in time sharing, batch processing, and transaction processing. It originally ran on VAX systems, and was later ported to the DEC Alpha and Intel Itanium.

History

In April, 1975, DIGITAL embarked on a hardware project, code named Star, to design on a 32-bit virtual address extension to its PDP-11. A companion software project, code named Starlet, was begun in June, 1975 to develop a totally new operating system, based on RSX-11M, for the Star family of processors. These two projects were tightly integrated from the beginning. Roger Gourd was the project lead for the Starlet program, with software engineers Dave Cutler, Dick Hustvedt, and Peter Lipman acting as the technical project leaders, each having responsibility for a different area of the operating system. The Star and Starlet projects culminated in the development the VAX 11/780 computer and the VAX-11/VMS operating system.

Over the years the name of the product has changed. In 1980 it was renamed, with version 2.0 release, to VAX/VMS (at the same time as the VAX-11 computer was renamed to simply VAX). In 1991 it was renamed again to OpenVMS to indicate its support for industry standards such as POSIX and Unix compatibility, and to drop the hardware connection as the port to DIGITAL's 64-bit Alpha RISC processor was in process. The OpenVMS name first appeared with the version 5.5 release.

Port to Alpha

The VMS port to Alpha necessitated the creation of a separate code streams for 32-bit and 64-bit architectures. 1992 saw the release of the first version of OpenVMS for Alpha AXP systems, designated OpenVMS AXP V1.0. (The decision to use the 1.x version numbering sream for the pre-production quality releases of OpenVMS AXP caused confusion for some customers and was not repeated in the subsequent porting program.)

In 1994, with the released of OpenVMS version 6.1, feature (and version number) parity between the VAX and Alpha variants was achieved. Subsequent version numberings for the VAX and Alpha variants of the product have remained consistent.

Port to Itanium

In 2001, just prior to its acquisition by HP, Compaq announced the port of OpenVMS to the Intel Itanium 64-bit EPIC architecture. This port was accomplished using the Alpha code stream which, together with the maturity of the VAX code stream, significantly simplified the porting process. Unlike the VAX to Alpha port, in which a "snapshot" of the VAX code base was used as the basis for the Alpha release, the Alpha and Itanium versions of OpenVMS are built using a common code base.

OpenVMS IA64 V8.0, the first pre-production quality release, was shipped in 2003. OpenVMS V8.2, the first production quality Itanium release, should ship in late 2004.

Features

OpenVMS can be divided into three layers:

• the kernel, made up of input/output, memory management, and process/time management subsystems.
• core services, made up of DCL, RMS, DECwindows (OpenVMS's X11 compliant windowing system), and the RTLs.
• utility programs for support, system management, and programming.

Clustering

OpenVMS supports clustering (called VAXcluster and later VMScluster), where multiple systems share processing, job queues, print queues, and disk storage, connected either by specialized hardware or Ethernet. An Ethernet-based cluster is called a LAVC, for local area network VMScluster. OpenVMS supports up to 96 nodes in a single cluster, and allows mixed-architecture clusters, where VAX and Alpha systems, or Alpha and Itanium systems can co-exist in a single cluster (OpenVMS Engineering has suggested that triple-architecture clusters are possible in theory, but are not supported by HP).

Common Language Environment

Among OpenVMS's notable features is the Common Language Environment, a strictly defined standard that specifies calling convention for functions and routines, including use of stack, registers, etc., independently of programming language. Because of this, it is possible to call a routine written in one language—such as FORTRAN—from another, such as C, without needing to know the implementation details of the target language. OpenVMS itself is implemented in a large variety of different languages (such as BLISS, VAX Macro, Ada, PL/I, C, Fortran, Basic, and several others), in contrast to a system such as Unix which is implemented nearly entirely in the C language.

Filesystem

OpenVMS has a very rich filesystem, with support for stream and record-oriented IO, ACLs, file versioning, etc. See OpenVMS filesystem.

OpenVMS Hobbyist

Despite being a commercial operating system, in 1997 OpenVMS and several layered products were made available free of charge for hobbyist, non-commercial use as part of the OpenVMS Hobbyist Program. Since then, several companies producing OpenVMS software have made their products available under the same terms, such as Process Software and DCL - Digital Command Language - command line interface.

• DECwindows - Digital's implementation of the X Window System.
• RMS - Record Management Services - high-level, language/device-independent IO.
• RTL - Runtime Libraries - shared routines and functions, callable from any language.
• FDL - File Description Language - defines file record/field structure.
• DECnet - Digital's proprietary networking architecture.

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