OpenVMS, often referred to as just VMS,
is a
multi-user
Multi-user software is computer software that allows access by multiple users of a computer. Time-sharing systems are multi-user systems. Most batch processing systems for mainframe computers may also be considered "multi-user", to avoid leaving t ...
,
multiprocessing
Multiprocessing is the use of two or more central processing units (CPUs) within a single computer system. The term also refers to the ability of a system to support more than one processor or the ability to allocate tasks between them. There ar ...
and
virtual memory
In computing, virtual memory, or virtual storage is a memory management technique that provides an "idealized abstraction of the storage resources that are actually available on a given machine" which "creates the illusion to users of a very l ...
-based
operating system
An operating system (OS) is system software that manages computer hardware, software resources, and provides common services for computer programs.
Time-sharing operating systems schedule tasks for efficient use of the system and may also in ...
. It is designed to support
time-sharing
In computing, time-sharing is the sharing of a computing resource among many users at the same time by means of multiprogramming and multi-tasking.DEC Timesharing (1965), by Peter Clark, The DEC Professional, Volume 1, Number 1
Its emergence a ...
,
batch processing
Computerized batch processing is a method of running software programs called jobs in batches automatically. While users are required to submit the jobs, no other interaction by the user is required to process the batch. Batches may automatically ...
,
transaction processing
Transaction processing is information processing in computer science that is divided into individual, indivisible operations called ''transactions''. Each transaction must succeed or fail as a complete unit; it can never be only partially comple ...
and
workstation
A workstation is a special computer designed for technical or scientific applications. Intended primarily to be used by a single user, they are commonly connected to a local area network and run multi-user operating systems. The term ''workstat ...
applications.
Customers using OpenVMS include banks and financial services, hospitals and healthcare, telecommunications operators, network information services, and industrial manufacturers. During the 1990s and 2000s, there were approximately half a million VMS systems in operation worldwide.
It was first announced by
Digital Equipment Corporation
Digital Equipment Corporation (DEC ), using the trademark Digital, was a major American company in the computer industry from the 1960s to the 1990s. The company was co-founded by Ken Olsen and Harlan Anderson in 1957. Olsen was president unt ...
(DEC) as VAX/VMS (''Virtual Address eXtension/Virtual Memory System'') alongside the
VAX-11/780
The VAX-11 is a discontinued family of 32-bit superminicomputers, running the Virtual Address eXtension (VAX) instruction set architecture (ISA), developed and manufactured by Digital Equipment Corporation (DEC). Development began in 1976. In ad ...
minicomputer in 1977.
OpenVMS has subsequently been
ported
In software engineering, porting is the process of adapting software for the purpose of achieving some form of execution in a computing environment that is different from the one that a given program (meant for such execution) was originally desi ...
to run on
DEC Alpha
Alpha (original name Alpha AXP) is a 64-bit reduced instruction set computer (RISC) instruction set architecture (ISA) developed by Digital Equipment Corporation (DEC). Alpha was designed to replace 32-bit VAX complex instruction set computers ...
systems, the
Itanium
Itanium ( ) is a discontinued family of 64-bit Intel microprocessors that implement the Intel Itanium architecture (formerly called IA-64). Launched in June 2001, Intel marketed the processors for enterprise servers and high-performance computin ...
-based
HPE Integrity Servers
HPE Integrity is a series of server computers produced by Hewlett Packard Enterprise (formerly Hewlett-Packard) since 2003, based on the Itanium processor. The Integrity brand name was inherited by HP from Tandem Computers via Compaq.
In 2015 ...
,
and select
x86-64
x86-64 (also known as x64, x86_64, AMD64, and Intel 64) is a 64-bit version of the x86 instruction set, first released in 1999. It introduced two new modes of operation, 64-bit mode and compatibility mode, along with a new 4-level paging mod ...
hardware and
hypervisor
A hypervisor (also known as a virtual machine monitor, VMM, or virtualizer) is a type of computer software, firmware or hardware that creates and runs virtual machines. A computer on which a hypervisor runs one or more virtual machines is calle ...
s.
Since 2014, OpenVMS is developed and supported by VMS Software Inc. (VSI).
OpenVMS offers
high availability
High availability (HA) is a characteristic of a system which aims to ensure an agreed level of operational performance, usually uptime, for a higher than normal period.
Modernization has resulted in an increased reliance on these systems. Fo ...
through
clustering — the ability to distribute the system over multiple physical machines.
[ This allows clustered applications and data to remain continuously available while operating system software and hardware maintenance and upgrades are performed, or if part of the cluster is destroyed. VMS cluster uptimes of 17 years have been reported.]
History
Origin and name changes
In April 1975, Digital Equipment Corporation
Digital Equipment Corporation (DEC ), using the trademark Digital, was a major American company in the computer industry from the 1960s to the 1990s. The company was co-founded by Ken Olsen and Harlan Anderson in 1957. Olsen was president unt ...
embarked on a project to design a 32-bit
In computer architecture, 32-bit computing refers to computer systems with a processor, memory, and other major system components that operate on data in 32-bit units. Compared to smaller bit widths, 32-bit computers can perform large calculation ...
extension to its PDP-11
The PDP-11 is a series of 16-bit minicomputers sold by Digital Equipment Corporation (DEC) from 1970 into the 1990s, one of a set of products in the Programmed Data Processor (PDP) series. In total, around 600,000 PDP-11s of all models were sold, ...
computer line. The hardware component was code named ''Star''; the operating system was code named ''Starlet''. Roger Gourd was the project lead for VMS. Software engineers Dave Cutler
David Neil Cutler Sr. (born March 13, 1942) is an American software engineer. He developed several computer operating systems, namely Microsoft's Windows NT, and Digital Equipment Corporation's RSX-11M, VAXELN, and VMS.
Personal history
Cutl ...
, Dick Hustvedt
Richard "Dick" Irvin Hustvedt (February 18, 1946 – April 15, 2008) was a renowned software engineer., designer and developer of several operating systems including Digital Equipment Corporation's RSX-11, and VMS.
Personal history
Hustvedt was ...
, and Peter Lipman acted as technical project leaders. The Star and Starlet projects culminated in the VAX-11/780
The VAX-11 is a discontinued family of 32-bit superminicomputers, running the Virtual Address eXtension (VAX) instruction set architecture (ISA), developed and manufactured by Digital Equipment Corporation (DEC). Development began in 1976. In ad ...
computer and the VAX/VMS operating system. The Starlet project's code name survives in VMS in the name of several of the system libraries, including STARLET.OLB
and STARLET.MLB
. VMS was mostly written in VAX MACRO
VAX MACRO is the computer assembly language implementing the VAX instruction set architecture for the OpenVMS operating system, originally released by Digital Equipment Corporation (DEC) in 1977.
The syntax, directives, macro language, and lexical ...
with some components written in BLISS
BLISS is a system programming language developed at Carnegie Mellon University (CMU) by W. A. Wulf, D. B. Russell, and A. N. Habermann around 1970. It was perhaps the best known system language until C debuted a few years later. Since then, C b ...
.
One of the original goals for VMS was backwards compatibility
Backward compatibility (sometimes known as backwards compatibility) is a property of an operating system, product, or technology that allows for interoperability with an older legacy system, or with input designed for such a system, especially i ...
with DEC's existing RSX-11M
RSX-11 is a discontinued family of multi-user real-time operating systems for PDP-11 computers created by Digital Equipment Corporation. In widespread use through the late 1970s and early 1980s, RSX-11 was influential in the development of later ...
operating system. Prior to the V3.0 release, VAX/VMS included an compatibility layer named the ''RSX Application Migration Executive'' (RSX AME) which allowed user mode RSX-11M software to be run unmodified on top of VMS. The RSX AME played an important role on early versions of VAX/VMS, which used re-used certain RSX-11M user mode utilities before native VAX versions had been developed. By the V3.0 release, all compatibility mode utilities were replaced with native implementations. In VAX/VMS V4.0, RSX AME was removed from the base system, and replaced with an optional layered product named ''VAX-11 RSX''.
A number of distributions of VAX/VMS were created:
* MicroVMS was a distribution of VAX/VMS designed for MicroVAX
The MicroVAX is a discontinued family of low-cost minicomputers developed and manufactured by Digital Equipment Corporation (DEC). The first model, the MicroVAX I, was introduced in 1983.(announced October 1983) They used processors that implemen ...
and VAXstation
The VAXstation is a discontinued family of workstation computers developed and manufactured by Digital Equipment Corporation using processors implementing the VAX instruction set architecture. VAXstation systems were typically shipped with either ...
hardware, which had less memory and disk space than larger VAX systems of the time. MicroVMS split up VAX/VMS into multiple kits, which a customer could use to install a subset of VAX/VMS tailored to their specific requirements. MicroVMS releases were produced for each of the V4.x releases of VAX/VMS and was discontinued when VAX/VMS V5.0 was released.
* Desktop-VMS was a short lived distribution of VAX/VMS sold with VAXstation
The VAXstation is a discontinued family of workstation computers developed and manufactured by Digital Equipment Corporation using processors implementing the VAX instruction set architecture. VAXstation systems were typically shipped with either ...
systems. It consisted of a single CD-ROM
A CD-ROM (, compact disc read-only memory) is a type of read-only memory consisting of a pre-pressed optical compact disc that contains data. Computers can read—but not write or erase—CD-ROMs. Some CDs, called enhanced CDs, hold both comput ...
containing a bundle of VMS, DECwindows, DECnet, VAXcluster support, and a setup process designed for non-technical users. Desktop-VMS could either be run directly from the CD, or could be installed onto a hard drive. Desktop-VMS had its own versioning scheme beginning with V1.0, which corresponded to the V5.x releases of VMS.
* An unofficial derivative of VAX/VMS named MOS VP (russian: Многофункциональная операционная система с виртуальной памятью, МОС ВП, lit=Multifunctional Operating System with Virtual Memory) was created in the Soviet Union
The Soviet Union,. officially the Union of Soviet Socialist Republics. (USSR),. was a transcontinental country that spanned much of Eurasia from 1922 to 1991. A flagship communist state, it was nominally a federal union of fifteen national ...
during the 1980s for the SM 1700 line of VAX clone hardware. MOS VP added support for the Cyrillic script
The Cyrillic script ( ), Slavonic script or the Slavic script, is a writing system used for various languages across Eurasia. It is the designated national script in various Slavic languages, Slavic, Turkic languages, Turkic, Mongolic languages, ...
, and translated parts of the user interface into Russian. Similar derivatives of MicroVMS known as ''MicroMOS VP'' (russian: МикроМОС ВП) or ''MOS-32M'' (russian: МОС-32М) were also created.
With the V5.0 release in April 1988, DEC began to refer to VAX/VMS as simply VMS in its documentation. In July 1992, DEC renamed VAX/VMS to OpenVMS as an indication for its support of open systems industry standards such as POSIX
The Portable Operating System Interface (POSIX) is a family of standards specified by the IEEE Computer Society for maintaining compatibility between operating systems. POSIX defines both the system- and user-level application programming interf ...
and Unix
Unix (; trademarked as UNIX) is a family of multitasking, multiuser computer operating systems that derive from the original AT&T Unix, whose development started in 1969 at the Bell Labs research center by Ken Thompson, Dennis Ritchie, and ot ...
compatibility, and to drop the VAX connection since a migration to a different architecture was underway. The OpenVMS name was first used with the OpenVMS AXP V1.0 release in November 1992. DEC began using the OpenVMS VAX name with the V6.0 release in June 1993.
Port to Alpha
During the 1980s, DEC planned to replace the VAX platform and the VMS operating system with the PRISM
Prism usually refers to:
* Prism (optics), a transparent optical component with flat surfaces that refract light
* Prism (geometry), a kind of polyhedron
Prism may also refer to:
Science and mathematics
* Prism (geology), a type of sedimentary ...
architecture and the MICA
Micas ( ) are a group of silicate minerals whose outstanding physical characteristic is that individual mica crystals can easily be split into extremely thin elastic plates. This characteristic is described as perfect basal cleavage. Mica is ...
operating system. When these projects were cancelled in 1988, a team was set up to design new VAX/VMS systems of comparable performance to RISC
In computer engineering, a reduced instruction set computer (RISC) is a computer designed to simplify the individual instructions given to the computer to accomplish tasks. Compared to the instructions given to a complex instruction set comput ...
-based Unix systems. After a number of failed attempts to design a faster VAX-compatible processor, the group demonstrated the feasibility of porting
In software engineering, porting is the process of adapting software for the purpose of achieving some form of execution in a computing environment that is different from the one that a given program (meant for such execution) was originally desi ...
VMS and its applications to a RISC architecture based on PRISM. This led to the creation of the Alpha
Alpha (uppercase , lowercase ; grc, ἄλφα, ''álpha'', or ell, άλφα, álfa) is the first letter of the Greek alphabet. In the system of Greek numerals, it has a value of one. Alpha is derived from the Phoenician letter aleph , whic ...
architecture. The project to port VMS to Alpha began in 1989, and first booted on a prototype Alpha EV3-based ''Alpha Demonstration Unit'' in early 1991.
The main challenge in porting VMS to a new architecture was that VMS and the VAX were designed together, meaning that VMS was dependent on certain details of the VAX architecture. Furthermore, a significant amount of the VMS kernel, layered products, and customer-developed applications were implemented in VAX MACRO
VAX MACRO is the computer assembly language implementing the VAX instruction set architecture for the OpenVMS operating system, originally released by Digital Equipment Corporation (DEC) in 1977.
The syntax, directives, macro language, and lexical ...
assembly code. Some of the changes needed to decouple VMS from the VAX architecture included the creation of the ''MACRO-32'' compiler, which treated VAX MACRO as a high-level language
In computer science, a high-level programming language is a programming language with strong abstraction from the details of the computer. In contrast to low-level programming languages, it may use natural language ''elements'', be easier to us ...
, and compiled it to Alpha object code
In computing, object code or object module is the product of a compiler.
In a general sense object code is a sequence of statements or instructions in a computer language, usually a machine code language (i.e., binary) or an intermediate langua ...
, and the emulation of certain low-level details of the VAX architecture in PALcode PALcode (Privileged Architecture Library code) is the name used by DEC in the Alpha instruction set architecture (ISA) for a set of functions in the System Reference Manual (SRM) or AlphaBIOS firmware, providing a hardware abstraction layer for ...
, such as interrupt handling
In digital computers, an interrupt (sometimes referred to as a trap) is a request for the processor to ''interrupt'' currently executing code (when permitted), so that the event can be processed in a timely manner. If the request is accepted, ...
and atomic queue instructions.
The VMS port to Alpha resulted in the creation of two separate codebases - one for VAX
VAX (an acronym for Virtual Address eXtension) is a series of computers featuring a 32-bit instruction set architecture (ISA) and virtual memory that was developed and sold by Digital Equipment Corporation (DEC) in the late 20th century. The VA ...
, and for Alpha. The Alpha code library was based on a snapshot of the VAX/VMS code base circa V5.4-2. 1992 saw the release of the first version of OpenVMS for Alpha AXP
Alpha (original name Alpha AXP) is a 64-bit reduced instruction set computer (RISC) instruction set architecture (ISA) developed by Digital Equipment Corporation (DEC). Alpha was designed to replace 32-bit VAX complex instruction set computers ( ...
systems, designated ''OpenVMS AXP V1.0''. In 1994, with the release of OpenVMS V6.1, feature (and version number) parity between the VAX and Alpha variants was achieved, this was the so-called Functional Equivalence release. The decision to use the 1.x version numbering stream for the pre-production quality releases of OpenVMS AXP caused confusion for some customers, and was not repeated in the subsequent ports of OpenVMS to new platforms.
When VMS was ported to Alpha, it was initially left as a 32-bit only operating system. This was done to ensure backwards compatibility with software written for the 32-bit VAX. 64-bit addressing was first added for Alpha in the V7.0 release. In order to allow 64-bit code to interoperate with older 32-bit code, OpenVMS does not create a distinction between 32-bit and 64-bit executables, but instead allows for both 32-bit and 64-bit pointers to be used within the same code. This is known as mixed pointer support. The 64-bit OpenVMS Alpha releases support a maximum virtual address space size of 8TiB (a 43-bit address space), which is the maximum supported by the Alpha 21064
The Alpha 21064 is a microprocessor developed and fabricated by Digital Equipment Corporation that implemented the Alpha (introduced as the Alpha AXP) instruction set architecture (ISA). It was introduced as the DECchip 21064 before it was renam ...
and Alpha 21164
The Alpha 21164, also known by its code name, EV5, is a microprocessor developed and fabricated by Digital Equipment Corporation that implemented the Alpha instruction set architecture (ISA). It was introduced in January 1995, succeeding the Alp ...
.
One of the more noteworthy Alpha-only features of OpenVMS was ''OpenVMS Galaxy'' - which allowed the partitioning of a single SMP server to run multiple instances of OpenVMS. Galaxy supported dynamic resource allocation to running partitions, and the ability to share memory between partitions.
Port to Intel Itanium
In 2001, prior to its acquisition by Hewlett-Packard
The Hewlett-Packard Company, commonly shortened to Hewlett-Packard ( ) or HP, was an American multinational information technology company headquartered in Palo Alto, California. HP developed and provided a wide variety of hardware components ...
, Compaq
Compaq Computer Corporation (sometimes abbreviated to CQ prior to a 2007 rebranding) was an American information technology company founded in 1982 that developed, sold, and supported computers and related products and services. Compaq produced ...
announced the port of OpenVMS to the Intel
Intel Corporation is an American multinational corporation and technology company headquartered in Santa Clara, California. It is the world's largest semiconductor chip manufacturer by revenue, and is one of the developers of the x86 seri ...
Itanium
Itanium ( ) is a discontinued family of 64-bit Intel microprocessors that implement the Intel Itanium architecture (formerly called IA-64). Launched in June 2001, Intel marketed the processors for enterprise servers and high-performance computin ...
architecture. The Itanium port was the result of Compaq's decision to discontinue future development of the Alpha architecture in favour of adopting the then-new Itanium architecture. The porting began in late 2001, and the first boot on took place on January 31, 2003. The first boot consisted of booting a minimal system configuration on a HP i2000 workstation, logging in as the SYSTEM
user, and running the DIRECTORY
command. The Itanium port of OpenVMS supports specific models and configurations of HPE Integrity Servers
HPE Integrity is a series of server computers produced by Hewlett Packard Enterprise (formerly Hewlett-Packard) since 2003, based on the Itanium processor. The Integrity brand name was inherited by HP from Tandem Computers via Compaq.
In 2015 ...
. The Itanium releases were originally named ''HP OpenVMS Industry Standard 64 for Integrity Servers'', although the names ''OpenVMS I64'' or ''OpenVMS for Integrity Servers'' are more commonly used.
The Itanium port was accomplished using source code maintained in common within the OpenVMS Alpha source code library, with the addition of conditional code and additional modules where changes specific to Itanium were required. This required certain architectural dependencies of OpenVMS to be replaced, or emulated in software. Some of the changes included using the Extensible Firmware Interface
UEFI (Unified Extensible Firmware Interface) is a set of specifications written by the UEFI Forum. They define the architecture of the platform firmware used for booting and its interface for interaction with the operating system. Examples of f ...
(EFI) to boot the operating system, reimplementing the functionality previously provided by Alpha PALcode inside the kernel, using new executable file formats (Executable and Linking Format
In computing, the Executable and Linkable FormatTool Interface Standard (TIS) Portable Formats SpecificationVersion 1.1'' (October 1993) (ELF, formerly named Extensible Linking Format), is a common standard file format for executable files, obj ...
and DWARF
Dwarf or dwarves may refer to:
Common uses
*Dwarf (folklore), a being from Germanic mythology and folklore
* Dwarf, a person or animal with dwarfism
Arts, entertainment, and media Fictional entities
* Dwarf (''Dungeons & Dragons''), a humanoid ...
), and adopting IEEE 754
The IEEE Standard for Floating-Point Arithmetic (IEEE 754) is a technical standard for floating-point arithmetic established in 1985 by the Institute of Electrical and Electronics Engineers (IEEE). The standard addressed many problems found i ...
as the default floating point format.
As with the VAX to Alpha port, a binary translator for Alpha to Itanium was made available, allowing user mode OpenVMS Alpha software to be ported to Itanium in situations where it was not possible to recompile the source code. This translator is known as the ''Alpha Environment Software Translator'' (AEST), and it also supported translating VAX executables which had already translated with VEST.
Two pre-production releases, OpenVMS I64 V8.0 and V8.1, were available on June 30, 2003, and on December 18, 2003. These releases were intended for HP organizations and third-party vendors involved with porting software packages to OpenVMS I64. The first production release, V8.2, was released in February 2005. V8.2 was also released for Alpha, subsequent V8.x releases of OpenVMS have maintained feature parity between the Alpha and Itanium architectures.
Port to x86-64
When VMS Software Inc. (VSI) announced that they had secured the rights to develop the OpenVMS operating system from HP, they also announced their intention to port OpenVMS to the x86-64
x86-64 (also known as x64, x86_64, AMD64, and Intel 64) is a 64-bit version of the x86 instruction set, first released in 1999. It introduced two new modes of operation, 64-bit mode and compatibility mode, along with a new 4-level paging mod ...
architecture. The porting effort ran concurrently with the establishment of the company, as well as the development of VSI's own Itanium and Alpha releases of OpenVMS V8.4-x.
The x86-64 port is targeted for specific servers from HPE and Dell
Dell is an American based technology company. It develops, sells, repairs, and supports computers and related products and services. Dell is owned by its parent company, Dell Technologies.
Dell sells personal computers (PCs), servers, data ...
, as well as certain virtual machine hypervisor
A hypervisor (also known as a virtual machine monitor, VMM, or virtualizer) is a type of computer software, firmware or hardware that creates and runs virtual machines. A computer on which a hypervisor runs one or more virtual machines is calle ...
s. Initial support was targeted for KVM and VirtualBox
Oracle VM VirtualBox (formerly Sun VirtualBox, Sun xVM VirtualBox and Innotek VirtualBox) is a type-2 hypervisor for x86 virtualization developed by Oracle Corporation.
VirtualBox was originally created by Innotek GmbH, which was acquired by ...
. Support for VMware
VMware, Inc. is an American cloud computing and virtualization technology company with headquarters in Palo Alto, California. VMware was the first commercially successful company to virtualize the x86 architecture.
VMware's desktop software ru ...
was announced in 2020, and Hyper-V
Microsoft Hyper-V, codenamed Viridian, and briefly known before its release as Windows Server Virtualization, is a native hypervisor; it can create virtual machines on x86-64 systems running Windows. Starting with Windows 8, Hyper-V superseded Win ...
has been described as a future target. In 2021, the x86-64 port was demonstrated running on an Intel Atom
Intel Atom is the brand name for a line of IA-32 and x86-64 instruction set ultra-low-voltage processors by Intel Corporation designed to reduce electric consumption and power dissipation in comparison with ordinary processors of the Intel Cor ...
-based single-board computer
A single-board computer (SBC) is a complete computer built on a single circuit board, with microprocessor(s), memory, input/output (I/O) and other features required of a functional computer. Single-board computers are commonly made as demonstrati ...
.
As with the Alpha and Itanium ports, the x86-64 port made some changes to simplify porting and supporting OpenVMS on the new platform including: replacing the proprietary GEM compiler backend used by the VMS compilers with LLVM
LLVM is a set of compiler and toolchain technologies that can be used to develop a front end for any programming language and a back end for any instruction set architecture. LLVM is designed around a language-independent intermediate represen ...
, changing the boot process so that OpenVMS is booted from a memory disk, and simulating the four privilege levels of OpenVMS in software since only two of x86-64's privilege levels are usable by OpenVMS.
The first boot was announced on May 14, 2019. This involved booting OpenVMS on VirtualBox, and successfully running the DIRECTORY
Directory may refer to:
* Directory (computing), or folder, a file system structure in which to store computer files
* Directory (OpenVMS command)
* Directory service, a software application for organizing information about a computer network's u ...
command. In May 2020, the V9.0 Early Adopter's Kit release was made available to a small number of customers. This consisted of the OpenVMS operating system running in a VirtualBox VM with certain limitations - most significantly, few layered products were available, and code can only be compiled for x86-64 using cross compilers which run on Itanium-based OpenVMS systems. Following the V9.0 release, VSI released a series of updates on a monthly or bimonthly basis which added additional functionality and hypervisor support. These were designated V9.0-A through V9.0-H. In June 2021, VSI released the V9.1 Field Test, making it available to VSI's customers and partners. V9.1 shipped as an ISO image
An optical disc image (or ISO image, from the ISO 9660 file system used with CD-ROM media) is a disk image that contains everything that would be written to an optical disc, disk sector by disc sector, including the optical disc file system. IS ...
which can be installed onto a variety of hypervisors, and onto HPE ProLiant DL380 servers starting with the V9.1-A release.
OpenVMS 9.2 for x86-64 reached General Availability on July 14, 2022.
Influence
During the 1980s, the MICA operating system for the PRISM architecture was intended to be the eventual successor to VMS. MICA was designed to maintain backwards compatibility with VMS applications while also supporting Ultrix
Ultrix (officially all-caps ULTRIX) is the brand name of Digital Equipment Corporation's (DEC) discontinued native Unix operating systems for the PDP-11, VAX, MicroVAX and DECstations.
History
The initial development of Unix occurred on DEC equip ...
applications on top of the same kernel. MICA was ultimately cancelled along with the rest of the PRISM platform, leading Dave Cutler to leave DEC for Microsoft. At Microsoft, Cutler led the creation of the Windows NT
Windows NT is a proprietary graphical operating system
An operating system (OS) is system software that manages computer hardware, software resources, and provides common services for computer programs.
Time-sharing operating systems sc ...
operating system, which was heavily inspired by the architecture of MICA. As a result, VMS is considered an ancestor of Windows NT
Windows NT is a proprietary graphical operating system
An operating system (OS) is system software that manages computer hardware, software resources, and provides common services for computer programs.
Time-sharing operating systems sc ...
, together with RSX-11
RSX-11 is a discontinued family of multi-user real-time operating systems for PDP-11 computers created by Digital Equipment Corporation. In widespread use through the late 1970s and early 1980s, RSX-11 was influential in the development of later ...
, VAXELN
VAXELN (typically pronounced "VAX-elan") is a discontinued real-time operating system for the VAX family of computers produced by the Digital Equipment Corporation (DEC) of Maynard, Massachusetts.
As with RSX-11 and VMS, Dave Cutler was the pri ...
and MICA, and many similarities exist between VMS and NT.
A now-defunct project named ''FreeVMS'' attempted to develop an open source
Open source is source code that is made freely available for possible modification and redistribution. Products include permission to use the source code, design documents, or content of the product. The open-source model is a decentralized sof ...
operating system following VMS conventions. FreeVMS was built on top of the L4 microkernel
L4 is a family of second-generation microkernels, used to implement a variety of types of operating systems (OS), though mostly for Unix-like, ''Portable Operating System Interface'' (POSIX) compliant types.
L4, like its predecessor microkernel ...
and supported the x86-64
x86-64 (also known as x64, x86_64, AMD64, and Intel 64) is a 64-bit version of the x86 instruction set, first released in 1999. It introduced two new modes of operation, 64-bit mode and compatibility mode, along with a new 4-level paging mod ...
architecture. Prior work investigating the implementation of VMS using a microkernel-based architecture had previously been undertaken as a prototyping exercise by DEC employees with assistance from Carnegie Mellon University
Carnegie Mellon University (CMU) is a private research university in Pittsburgh, Pennsylvania. One of its predecessors was established in 1900 by Andrew Carnegie as the Carnegie Technical Schools; it became the Carnegie Institute of Technology ...
using the Mach 3.0 microkernel ported to VAXstation 3100 hardware, adopting a multiserver architectural model.
Architecture
The OpenVMS operating system has a layered architecture, consisting of a privileged ''Executive'', an intermediately-privileged Command Language Interpreter, and unprivileged utilities and run-time libraries (RTLs). Unprivileged code typically invokes the functionality of the Executive through ''system services'' (equivalent to system calls
In computing, a system call (commonly abbreviated to syscall) is the programmatic way in which a computer program requests a service from the operating system on which it is executed. This may include hardware-related services (for example, acc ...
in other operating systems).
OpenVMS' layers and mechanisms are built around certain features of the VAX architecture, including:
* The availability of four processor access modes (named ''Kernel'', ''Executive'', ''Supervisor'' and ''User'', in order of decreasing privilege). Each mode has its own stack, and each memory page
A page, memory page, or virtual page is a fixed-length contiguous block of virtual memory, described by a single entry in the page table. It is the smallest unit of data for memory management in a virtual memory operating system. Similarly, a p ...
can have memory protection
Memory protection is a way to control memory access rights on a computer, and is a part of most modern instruction set architectures and operating systems. The main purpose of memory protection is to prevent a process from accessing memory that ha ...
s specified per-mode.
* A virtual address space
In computing, a virtual address space (VAS) or address space is the set of ranges of virtual addresses that an operating system makes available to a process. The range of virtual addresses usually starts at a low address and can extend to the hig ...
which is partitioned between process-private space sections, and system space sections which are common to all processes.
* 32 interrupt priority level
The interrupt priority level (IPL) is a part of the current system interrupt state, which indicates the interrupt requests that will currently be accepted. The IPL may be indicated in hardware by the registers in a Programmable Interrupt Controlle ...
s which are used for synchronization
Synchronization is the coordination of events to operate a system in unison. For example, the conductor of an orchestra keeps the orchestra synchronized or ''in time''. Systems that operate with all parts in synchrony are said to be synchronou ...
.
* Hardware support for delivering asynchronous system trap
Asynchronous System Trap (AST) refers to a mechanism used in several computer operating systems designed by the former Digital Equipment Corporation (DEC) of Maynard, Massachusetts.
Mechanism
Various events within these systems can be optionally ...
s to processes.
These VAX architecture mechanisms are implemented on Alpha, Itanium and x86-64 by either mapping to corresponding hardware mechanisms on those architectures, or through emulation (via PALcode PALcode (Privileged Architecture Library code) is the name used by DEC in the Alpha instruction set architecture (ISA) for a set of functions in the System Reference Manual (SRM) or AlphaBIOS firmware, providing a hardware abstraction layer for ...
on Alpha, or in software on Itanium and x86-64).
Executive and Kernel
The OpenVMS Executive comprises the privileged code and data structures which reside in the system space. The Executive is further subdivided between the ''Kernel'', which consists of the code which runs at the kernel access mode, and the less-privileged code outside of the Kernel which runs at the executive access mode.
The components of the Executive which run at executive access mode include the Record Management Services
Record Management Services (RMS) are procedures in the VMS, RSTS/E, RT-11 and RSX-11M operating systems that programs may call to process files and records within files.
Its file formats and procedures are similar to of those in some IBM access ...
, and certain system services such as image activation. The main distinction between the kernel and executive access modes is that most of the operating system's core data structures can be read from executive mode, but require kernel mode to be written to. Code running at executive mode can switch to kernel mode at will, meaning that the barrier between the kernel and executive modes is intended as a safeguard against accidental corruption as opposed to a security mechanism.
The Kernel
Kernel may refer to:
Computing
* Kernel (operating system), the central component of most operating systems
* Kernel (image processing), a matrix used for image convolution
* Compute kernel, in GPGPU programming
* Kernel method, in machine learnin ...
comprises the operating system's core data structures (e.g. page tables, the I/O database and scheduling data), and the routines which operate on these structures. The Kernel is typically described as having three major subsystems: I/O, Process and Time Management, Memory Management. In addition, other functionality such as logical name management, synchronization and system service dispatch are implemented inside the Kernel.
OpenVMS allows user mode code with suitable privileges to switch to executive or kernel mode using the $CMEXEC
and $CMKRNL
system services, respectively. This allows code outside of system space to have direct access to the Executive's routines and system services. In addition to allowing third-party extensions to the operating system, Privileged Images are used by core operating system utilities to manipulate operating system data structures through undocumented interfaces.
File system
The typical user and application interface into the file system
In computing, file system or filesystem (often abbreviated to fs) is a method and data structure that the operating system uses to control how data is stored and retrieved. Without a file system, data placed in a storage medium would be one larg ...
is the Record Management Services
Record Management Services (RMS) are procedures in the VMS, RSTS/E, RT-11 and RSX-11M operating systems that programs may call to process files and records within files.
Its file formats and procedures are similar to of those in some IBM access ...
(RMS), although applications can interface directly with the underlying file system through the QIO
QIO (Queue I/O) is a term used in several computer operating systems designed by the former Digital Equipment Corporation ( DEC) of Maynard, Massachusetts.
I/O operations on these systems are initiated by issuing a QIO call to the kernel. There ...
system services. The file systems supported by VMS are referred to as the Files-11
Files-11 is the file system used by Digital Equipment Corporation OpenVMS operating system, and also (in a simpler form) by the older RSX-11. It is a hierarchical file system, with support for access control lists, record-oriented I/O, remote ...
''On-Disk Structures'' (ODS), the most significant of which are ''ODS-2'' and ''ODS-5''. VMS is also capable of accessing files on ISO 9660
ISO 9660 (also known as ECMA-119) is a file system for optical disc media. Being sold by the International Organization for Standardization (ISO) the file system is considered an international technical standard. Since the specification is av ...
CD-ROM
A CD-ROM (, compact disc read-only memory) is a type of read-only memory consisting of a pre-pressed optical compact disc that contains data. Computers can read—but not write or erase—CD-ROMs. Some CDs, called enhanced CDs, hold both comput ...
s and magnetic tape
Magnetic tape is a medium for magnetic storage made of a thin, magnetizable coating on a long, narrow strip of plastic film. It was developed in Germany in 1928, based on the earlier magnetic wire recording from Denmark. Devices that use magne ...
with ANSI tape labels.
Files-11 is limited to 2TiB volumes. DEC attempted to replace it with a log-structured file system
A log-structured filesystem is a file system in which data and metadata are written sequentially to a circular buffer, called a log. The design was first proposed in 1988 by John K. Ousterhout and Fred Douglis and first implemented in 1992 by Ou ...
file system named Spiralog first released in 1995. However, Spiralog was discontinued due to a variety of problems, including issues with handling full volumes. Instead, there has been discussion of porting the open source GFS2 file system to OpenVMS.
Command Language Interpreter
An OpenVMS Command Language Interpreter (CLI) implements a command line interface
A command-line interpreter or command-line processor uses a command-line interface (CLI) to receive commands from a user in the form of lines of text. This provides a means of setting parameters for the environment, invoking executables and pro ...
for OpenVMS; responsible for executing individual commands, as well as ''command procedures'' (equivalent to shell script
A shell script is a computer program designed to be run by a Unix shell, a command-line interpreter. The various dialects of shell scripts are considered to be scripting languages. Typical operations performed by shell scripts include file manip ...
s or batch file
Batch may refer to:
Food and drink
* Batch (alcohol), an alcoholic fruit beverage
* Batch loaf, a type of bread popular in Ireland
* A dialect term for a bread roll used in North Warwickshire, Nuneaton and Coventry, as well as on the Wirral ...
s). The standard CLI for OpenVMS is the DIGITAL Command Language
DIGITAL Command Language (DCL) is the standard command language adopted by many of the operating systems created by Digital Equipment Corporation. DCL had its roots in IAS, TOPS-20, and RT-11 and was implemented as a standard across most of Digit ...
, although other options are available as well.
Unlike Unix shell
A Unix shell is a command-line Interpreter (computing), interpreter or shell (computing), shell that provides a command line user interface for Unix-like operating systems. The shell is both an interactive command language and a scripting langua ...
s, which typically run in their own isolated process and behave like any other user mode program, OpenVMS CLIs are an optional component of a process, which exist alongside any executable image which that process may run. Whereas a Unix shell will typically run executables by creating a separate process using fork-exec, an OpenVMS CLI will typically load the executable image into the same process, transfer control to the image, and ensure that control is transferred back to CLI once the image has exited and that the process is returned to its original state.
Due to the fact that the CLI is loaded into the same address space as user code, and that the CLI is responsible for invoking image activation and image rundown, the CLI is mapped into the process address space at supervisor access mode - a higher level of privilege than most user code. This is in order to prevent accidental or malicious manipulation of the CLI's code and data structures by user mode code.
Features
Clustering
OpenVMS supports clustering (first called ''VAXcluster'' and later ''VMScluster''), where multiple computers run their own instance of the operating system. Clustered computers (nodes) may be fully independent from each other, or they may share devices like disk drives and printers. Communication across nodes provides a single system image In distributed computing, a single system image (SSI) cluster is a cluster of machines that appears to be one single system. The concept is often considered synonymous with that of a distributed operating system, but a single image may be presented ...
abstraction. Nodes may be connected to each other via a proprietary hardware connection called Cluster Interconnect or via a standard Ethernet
Ethernet () is a family of wired computer networking technologies commonly used in local area networks (LAN), metropolitan area networks (MAN) and wide area networks (WAN). It was commercially introduced in 1980 and first standardized in 198 ...
LAN.
OpenVMS supports up to 96 nodes in a single cluster. It also allows mixed-architecture clusters. (VAX, Alpha, and Itanium computers each have a different architecture.) OpenVMS clusters allow applications to function during planned or unplanned outages. Planned outages include hardware and software upgrades.
Networking
The DECnet
DECnet is a suite of network protocols created by Digital Equipment Corporation. Originally released in 1975 in order to connect two PDP-11 minicomputers, it evolved into one of the first peer-to-peer network architectures, thus transforming DEC ...
protocol suite is tightly integrated into VMS, allowing remote logins, as well as transparent access to files, printers and other resources on VMS systems over a network. Modern versions of VMS support both the traditional Phase IV DECnet protocol, as well as the OSI-compatible Phase V (also known as ''DECnet-Plus''). Support for TCP/IP
The Internet protocol suite, commonly known as TCP/IP, is a framework for organizing the set of communication protocols used in the Internet and similar computer networks according to functional criteria. The foundational protocols in the suit ...
is provided by the optional ''TCP/IP Services for OpenVMS'' layered product (originally known as the ''VMS/ULTRIX Connection'', then as the ''ULTRIX
Ultrix (officially all-caps ULTRIX) is the brand name of Digital Equipment Corporation's (DEC) discontinued native Unix operating systems for the PDP-11, VAX, MicroVAX and DECstations.
History
The initial development of Unix occurred on DEC equip ...
Communications Extensions'' or UCX). TCP/IP Services is based on a port of the BSD
The Berkeley Software Distribution or Berkeley Standard Distribution (BSD) is a discontinued operating system based on Research Unix, developed and distributed by the Computer Systems Research Group (CSRG) at the University of California, Berk ...
network stack to OpenVMS, along with support for common protocols such as SSH
The Secure Shell Protocol (SSH) is a cryptographic network protocol for operating network services securely over an unsecured network. Its most notable applications are remote login and command-line execution.
SSH applications are based on a ...
, DHCP
The Dynamic Host Configuration Protocol (DHCP) is a network management protocol used on Internet Protocol (IP) networks for automatically assigning IP addresses and other communication parameters to devices connected to the network using a cli ...
, FTP
The File Transfer Protocol (FTP) is a standard communication protocol used for the transfer of computer files from a server to a client on a computer network. FTP is built on a client–server model architecture using separate control and data ...
and SMTP
The Simple Mail Transfer Protocol (SMTP) is an Internet standard communication protocol for electronic mail transmission. Mail servers and other message transfer agents use SMTP to send and receive mail messages. User-level email clients typical ...
.
DEC sold a software package named PATHWORKS
PATHWORKS (it was usually written in all caps) was the trade name used by Digital Equipment Corporation of Maynard, Massachusetts for a series of programs that eased the interoperation of Digital's minicomputers and servers with personal computer ...
(originally known as the ''Personal Computer Systems Architecture'' or PCSA) which allowed personal computer
A personal computer (PC) is a multi-purpose microcomputer whose size, capabilities, and price make it feasible for individual use. Personal computers are intended to be operated directly by an end user, rather than by a computer expert or tec ...
s running MS-DOS
MS-DOS ( ; acronym for Microsoft Disk Operating System, also known as Microsoft DOS) is an operating system for x86-based personal computers mostly developed by Microsoft. Collectively, MS-DOS, its rebranding as IBM PC DOS, and a few ope ...
, Microsoft Windows
Windows is a group of several proprietary graphical operating system families developed and marketed by Microsoft. Each family caters to a certain sector of the computing industry. For example, Windows NT for consumers, Windows Server for serv ...
or OS/2
OS/2 (Operating System/2) is a series of computer operating systems, initially created by Microsoft and IBM under the leadership of IBM software designer Ed Iacobucci. As a result of a feud between the two companies over how to position OS/2 ...
, or the Apple Macintosh
The Mac (known as Macintosh until 1999) is a family of personal computers designed and marketed by Apple Inc. Macs are known for their ease of use and minimalist designs, and are popular among students, creative professionals, and software en ...
to serve as a terminal for VMS systems, or to use VMS systems as a file or print server. PATHWORKS was later renamed to ''Advanced Server for OpenVMS'', and was eventually replaced with a VMS port of Samba
Samba (), also known as samba urbano carioca (''urban Carioca samba'') or simply samba carioca (''Carioca samba''), is a Brazilian music genre that originated in the Afro-Brazilian communities of Rio de Janeiro in the early 20th century. Havin ...
at the time of the Itanium port.
DEC provided the Local Area Transport Local Area Transport (LAT) is a non-routable (data link layer) networking technology developed by Digital Equipment Corporation to provide connection between the DECserver terminal servers and Digital's VAX and Alpha and MIPS host computers via Et ...
(LAT) protocol which allowed remote terminals and printers to be attached to a VMS system through a terminal server
A terminal server connects devices with a serial port to a local area network (LAN). Products marketed as terminal servers can be very simple devices that do not offer any security functionality, such as data encryption and user authentication. ...
such as one of the DECserver
In computer networking, DECserver initially referred to a highly successful family of asynchronous console server / terminal server / print server products introduced by Digital Equipment Corporation (DEC) and later referred to a class of UNIX-vari ...
family.
Programming
DEC (and its successor companies) provided a wide variety of programming languages for VMS. Officially supported languages on VMS, either current or historical, include:
* VAX MACRO
VAX MACRO is the computer assembly language implementing the VAX instruction set architecture for the OpenVMS operating system, originally released by Digital Equipment Corporation (DEC) in 1977.
The syntax, directives, macro language, and lexical ...
* BLISS
BLISS is a system programming language developed at Carnegie Mellon University (CMU) by W. A. Wulf, D. B. Russell, and A. N. Habermann around 1970. It was perhaps the best known system language until C debuted a few years later. Since then, C b ...
* C
* DCL
* Fortran
* Pascal
Pascal, Pascal's or PASCAL may refer to:
People and fictional characters
* Pascal (given name), including a list of people with the name
* Pascal (surname), including a list of people and fictional characters with the name
** Blaise Pascal, Fren ...
* COBOL
* BASIC
* C++
* Java (programming language), Java
* Common Lisp
* APL (programming language), APL
* Ada (programming language), Ada
* PL/I
* DIBOL
* CORAL
* OPS5
* IBM RPG II, RPG II
* MUMPS
* MACRO-11
* DEC Text Processing Utility, DECTPU
* VAX SCAN
Among OpenVMS's notable features is the ''Common Language Environment'', a strictly defined standard that specifies calling conventions for functions and routines, including use of stack (abstract data type), stacks, processor register, registers, etc., independent of programming language. Because of this, it is possible to call a routine written in one language (for example, Fortran) from another (for example, COBOL), without needing to know the implementation details of the target language. OpenVMS itself is implemented in a variety of different languages and the common language environment and calling standard supports freely mixing these languages. DEC created a tool named the ''Structure Definition Language'' (SDL), which allowed data type definitions to be generated for different languages from a common definition.
Development Tools
DEC provided a collection of software development tools in a layered product named ''DECset'' (originally named ''VAXset''). This consisted of the following tools:
* Language-Sensitive Editor (LSE)
* ''Code Management System'' (CMS) a version control system
* ''Module Management System'' (MMS), a build automation, build tool
* the ''Source Code Analyzer (''SCA), a static analyzer
* the ''Performance and Coverage Analyzer'' (''PCA''), a Profiling (computer programming), profiler
* ''Digital Test Manager'' (DTM), as a test manager
* In addition, a number of text editors are included in the operating system, including EDT (Digital), EDT, EVE (text editor), EVE and TECO (text editor), TECO.
The OpenVMS Debugger supports all DEC compilers and many third party languages. It allows breakpoints, watchpoints and interactive runtime program debugging either using a command line interface, command line or graphical user interface. A pair of lower-level debuggers, named ''DELTA'' and ''XDELTA'', can be used to debug privileged code in additional to normal application code.
In 2019, VSI released an officially-supported Integrated Development Environment for VMS based on Visual Studio Code. This allows VMS applications to be developed and debugged remotely from a Microsoft Windows
Windows is a group of several proprietary graphical operating system families developed and marketed by Microsoft. Each family caters to a certain sector of the computing industry. For example, Windows NT for consumers, Windows Server for serv ...
, macOS or Linux workstation.
Database management
DEC created a number of optional database products for VMS, some of which were marketed as the ''VAX Information Architecture'' family. These products included:
* Oracle Rdb, Rdb – A relational database system which originally used the proprietary ''Relational Data Operator'' (RDO) query interface, but later gained SQL support.
* ''DBMS'' – A database management system which uses the CODASYL Network database model, network model and ''Data Manipulation Language'' (DML).
* Digital Standard MUMPS (DSM) – an integrated programming language and key-value database.
* ''Common Data Dictionary'' (CDD) – a central database schema repository, which allowed schemas to be shared between different applications, and data definitions to be generated for different programming languages.
* DATATRIEVE – a query and reporting tool which could access data from RMS files as well as Rdb and DBMS databases.
* Application Control Management System (ACMS) – A transaction processing monitor, which allows applications to be created using a high-level ''Task Description Language'' (TDL). Individual steps of a transaction can be implemented using DCL commands, or Common Language Environment procedures. User interfaces can be implemented using TDMS, DECforms or Digital's ALL-IN-1 office automation product.
* ''RALLY'', ''DECadmire'' – Fourth-generation programming languages (4GLs) for generating database-backed applications. DECadmire featured integration with ACMS, and later provided support for generating Visual Basic client-server applications for Windows PCs.
In 1994, DEC sold Rdb, DBMS and CDD to Oracle Corporation, Oracle, where they remain under active development. In 1995, DEC sold DSM to InterSystems, who renamed it ''Open M'', and eventually replaced it with their InterSystems Caché, Caché product.
Examples of third-party database management systems for OpenVMS include MariaDB, Mimer SQL and System 1032.
User interfaces
VMS was originally designed to be used and managed interactively using DEC's text-based video terminals such as the VT100, or hardcopy terminals such as the DECwriter series. Since the introduction of the VAXstation
The VAXstation is a discontinued family of workstation computers developed and manufactured by Digital Equipment Corporation using processors implementing the VAX instruction set architecture. VAXstation systems were typically shipped with either ...
line in 1984, VMS has optionally supported graphical user interfaces for use with workstations or X terminals such as the VT1000 series.
Text-based user interfaces
The DIGITAL Command Language
DIGITAL Command Language (DCL) is the standard command language adopted by many of the operating systems created by Digital Equipment Corporation. DCL had its roots in IAS, TOPS-20, and RT-11 and was implemented as a standard across most of Digit ...
(DCL), has served as the primary command language interpreter (CLI) of OpenVMS since the first release. Other official CLIs available for VMS include the RSX-11
RSX-11 is a discontinued family of multi-user real-time operating systems for PDP-11 computers created by Digital Equipment Corporation. In widespread use through the late 1970s and early 1980s, RSX-11 was influential in the development of later ...
MCR (VAX only), and various Unix shell
A Unix shell is a command-line Interpreter (computing), interpreter or shell (computing), shell that provides a command line user interface for Unix-like operating systems. The shell is both an interactive command language and a scripting langua ...
s. DEC provided tools for creating text-based user interface applications – the ''Form Management System'' (FMS) and ''Terminal Data Management System'' (TDMS), later succeeded by ''DECforms''. A lower level interface named ''Screen Management Services'' (SMG$), comparable to Unix curses (programming library), curses, also exists.
Graphical user interfaces
Over the years, VMS has gone through a number of different GUI toolkits and interfaces:
* The original graphical user interface for VMS was a proprietary windowing system known as the ''VMS Workstation Software'' (VWS), which was first released for the VAXstation#VAXstation I, VAXstation I in 1984. It exposed an API called the User Interface Services (UIS). It ran on a limited selection of VAX hardware.
* In 1989, DEC replaced VWS with a new X11-based windowing system named ''DECwindows''. It was first included in VAX/VMS V5.1. Early versions of DECwindows featured an interface built on top of a proprietary toolkit named the ''X User Interface'' (XUI). A layered product named UISX was provided to allow VWS/UIS applications to run on top of DECwindows. Parts of XUI were subsequently used by the Open Software Foundation as the foundation of the Motif toolkit.
* In 1991, DEC replaced XUI with the Motif toolkit, creating ''DECwindows Motif''. As a result, the Motif Window Manager became the default DECwindows interface in OpenVMS V6.0, although the XUI window manager remained as an option.
* In 1996, as part of OpenVMS V7.1, DEC released the ''New Desktop'' interface for DECwindows Motif, based on the Common Desktop Environment (CDE). On Alpha and Itanium systems, it is still possible to select the older MWM-based UI (referred to as the "DECwindows Desktop") at login time. The New Desktop was never ported to the VAX releases of OpenVMS.
Versions of VMS running on DEC Alpha workstations in the 1990s supported OpenGL and Accelerated Graphics Port (AGP) graphics adapters. VMS also provides support for older graphics standards such as Graphical Kernel System, GKS and PHIGS. Modern versions of DECwindows are based on X.Org Server.
Security
OpenVMS provides various security features and mechanisms, including security identifiers, resource identifiers, subsystem identifiers, Access control list, ACLs, intrusion detection and detailed security auditing and alarms. Specific versions evaluated at Trusted Computer System Evaluation Criteria Class C2 and, with the SEVMS security enhanced release at Class B1. OpenVMS also holds an ITSEC E3 rating (see National Computer Security Center, NCSC and Common Criteria). Passwords are hashed using the George B. Purdy#The Purdy polynomial, Purdy Polynomial.
Vulnerabilities
* Early versions of VMS included a number of privileged user accounts (including SYSTEM
, FIELD
, SYSTEST
and DECNET
) with default passwords which were often left unchanged by system managers. A number of computer worms for VMS including the WANK (computer worm), WANK worm and the Father Christmas (computer worm), Father Christmas worm exploited these default passwords to gain access to nodes on DECnet networks. This issue was also described by Clifford Stoll in ''The Cuckoo's Egg (book), The Cuckoo's Egg'' as a means by which Markus Hess gained unauthorized access to VAX/VMS systems. In V5.0, the default passwords were removed, and it became mandatory to provide passwords for these accounts during system setup.
* A 33-year-old vulnerability in VMS on VAX and Alpha was discovered in 2017 and assigned the CVE ID . On the affected platforms, this vulnerability allowed an attacker with access to the DCL command line to carry out a privilege escalation attack. The vulnerability relies on exploiting a buffer overflow bug in the DCL command processing code, the ability for a user to interrupt a running image (program executable) with and return to the DCL prompt, and the fact that DCL retains the privileges of the interrupted image. The buffer overflow bug allowed shellcode to be executed with the privileges of an interrupted image. This could be used in conjunction with an image installed with higher privileges than the attacker's account to bypass system security.
POSIX compatibility
Various official Unix
Unix (; trademarked as UNIX) is a family of multitasking, multiuser computer operating systems that derive from the original AT&T Unix, whose development started in 1969 at the Bell Labs research center by Ken Thompson, Dennis Ritchie, and ot ...
and POSIX
The Portable Operating System Interface (POSIX) is a family of standards specified by the IEEE Computer Society for maintaining compatibility between operating systems. POSIX defines both the system- and user-level application programming interf ...
compatibility layers were created for VMS. The first of which was ''DEC/Shell'' - which was a layered product consisting of ports of the Version 7 Unix Bourne shell and several other Unix utilities to VAX/VMS. In 1992, DEC released the ''POSIX for OpenVMS'' layered product, which included a shell based on the Korn Shell. POSIX for OpenVMS was later replaced by the open source ''GNV'' (GNU's not VMS) project, which was first included in OpenVMS media in 2002. Amongst other GNU tools, GNV includes a port of the Bash (Unix shell), Bash shell to VMS. Examples of third party Unix compatibility layers for VMS include Eunice (software), Eunice.
Hobbyist programs
In 1997 OpenVMS and a number of 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. Prior to the x86-64 port, the age and cost of hardware capable of running OpenVMS made emulators such as SIMH a common choice for hobbyist installations.
In March 2020, HPE announced the end of the OpenVMS Hobbyist Program. This was followed by VSI's announcement of the ''Community License Program'' (CLP) in April 2020, which was intended as a replacement for the HPE Hobbyist Program. The CLP was launched in July 2020, and provides licenses for VSI OpenVMS releases on Alpha and Integrity systems. OpenVMS x86-64 licenses will be made available when a stable version is released for this architecture. OpenVMS for VAX is not covered by the CLP, since there are no VSI releases of OpenVMS VAX, and the old versions are still owned by HPE.
Release history
See also
* Comparison of operating systems
* Terry Shannon (IT), Terry Shannon
* Event flag
References
Further reading
*Getting Started with OpenVMS, Michael D. Duffy,
*Introduction to OpenVMS, 5th Edition, Lesley Ogilvie Rice,
*
*OpenVMS Alpha Internals and Data Structures: Memory Management, Ruth Goldenberg,
*OpenVMS Alpha Internals and Data Structures : Scheduling and Process Control : Version 7.0, Ruth Goldenberg, Saro Saravanan, Denise Dumas,
*VAX/VMS Internals and Data Structures: Version 5.2 ("IDSM"), Ruth Goldenberg, Saro Saravanan, Denise Dumas,
*Writing Real Programs in DCL, second edition, Stephen Hoffman, Paul Anagnostopoulos,
*Writing OpenVMS Alpha Device Drivers in C, Margie Sherlock, Leonard Szubowicz,
*OpenVMS Performance Management, Joginder Sethi,
*Getting Started with OpenVMS System Management, 2nd Edition, David Donald Miller, Stephen Hoffman, Lawrence Baldwin,
*The OpenVMS User's Guide, Second Edition, Patrick Holmay,
*Using DECwindows Motif for OpenVMS, Margie Sherlock,
*
*The hitchhiker's guide to VMS : an unsupported-undocumented-can-go-away-at-any-time feature of VMS, Bruce Ellis,
*
External links
VMS Software: Current Roadmap and Future Releases
VMS Software: Documentation
*
*[news://comp.os.vms/ comp.os.vms Usenet group], archives o
Google Groups
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Fault-tolerant computer systems
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