Open Virtual Memory System (OpenVMS)

OpenVMS was originally just called Virtual Memory System (VMS), but it was changed to OpenVMS when it was retooled to work for the Alpha processor family. The "Open" does not denote open source but rather it suggests the new added support for UNIX-like interfaces from the Portable Operating System Interface (POSIX) standard which includes standard C functions that can be ported to any POSIX-supporting system.

OpenVMS supports multi-user, time-sharing, batch, real-time and transaction processing through the use of virtual memory and offers high availability through clustering by distributing the system over many physical machines. Clustering allows the system to be somewhat disaster tolerant as it can still function even when individual data processing facilities become unavailable.

OpenVMS also pioneered many features that are now standard on high-end server operating systems like:

• Integrated networking
• Integrated database features as record management services (RMS)
• Layered databases like relational databases
• Distributed file system
• Symmetrical, asymmetrical, and non-uniform memory access (NUMA) multiprocessing
• Clustering
• Shell command language
• High level of security
• Hardware partitioning for multiprocessors
• Multiple programming language support with standardized interoperability mechanism calls between those languages