Open VMS is an operating system that started out on Digital Equipment Corporations first produced systems such as the PDP. The migration through the years was to VAX and Alpha systems. VMS has a file system that supports fairly long names, is heirarchical in directory structure and supports multiple versions of the same file, with the same name. It has been used and developed through the years to it's current version 7.3. It will be ported to the 64 bit Itanium processor family within the next 3-4 years. I have been a system manager for over 15 years on these systems, and they are very reliable and fault tolerant.

For a manager, OpenVMS can be a bear to maintain but as a longtime user, it is a beautiful OS.

Open VMS released after VMS. It is less centric to DEC products, i.e. it will support non-DEC products/OS and their integration to a larger extent.