(X.25 only when equipped with the optional NIO.) Websphere MQ 6.0 (a.k.a. MQ Series) is TCP/IP based; so, that is also supported by ftServer hardware. Devices supporting the legacy protocols run on the Continuum hardware and may be accessed from current hardware over the Open StrataLINK network. Fault tolerance Fault tolerance is built into VOS from the bottom up. On a hardware level, major devices are run in lockstepped duplex mode, meaning that there are two identical devices performing the same action at the same time. (In addition, each device, or board, is also duplexed in order to identify internal board failures at a hardware level, which is why Stratus hardware can be defined as "lock stepped".) These boards are actively monitored by the operating system which can correct any minor inconsistencies (such as bad disk-writes or reads). Any boards which report an unacceptable number of faults are removed from service by the system; the duplexed board will continue operation until the problem is resolved via a hot-fix. This includes CPUs, disk drives, and any other device that can logically be duplexed (which by definition, excludes communications devices). The system will continue processing as normal and will automatically raise a fault ticket with Stratus Customer Service via RSN (the Remote Service Network). Stratus Customer Service will then dial into the system using RSN to investigate the problem and dispatch replacement parts. The operating system is designed to avoid crashes due to a simplexed hardware failure. File system VOS supports a number of unique file types: Stream files: a stream of binary data, corresponding directly with the concept of a file on other operating systems. Fixed files: a sequence of records of a fixed size. Relative files: a sequence of records of a fixed file supporting random access Sequential files: a sequence of records of variable size Queue files: file-system based backup for message queues Pipes: named pipes for inter-process communication Transaction files: these provide support for journal based rollback The VOS API allows the creation of multiple indexes per file, sorting according to the contents of a record, or an external key, or an internal key, or a well-defined set of multiple keys. A VOS file with one or more indexes can be used as a C-ISAM database table. VOS uses a proprietary file naming syntax which includes the system name, module name, disk number, and directory, with components separated