OpenExtensions for z/VM

Byte File Systems

An OpenExtensions user can create, store, and access the Byte File Systems familiar to UNIX users (and similar to the file systems of DOS and OS/2 and to the hierarchical file system of OS/390).

Byte File System Characteristics

With the Byte File System support provided by OpenExtensions for z/VM services:

• Filenames and pathnames can be much longer than with traditional CMS file identifiers.
• Terminals and communication pipes are accessed as files.
• The Byte structure encourages an enterprise and its users to organize sets of files in a natural way (for example, by area, by department, by group of users, by user, and so forth).

OpenExtensions for z/VM services provide facilities to make accessible (or remove from accessibility) different subsets of files in any Byte structure by logically mounting any particular hierarchy. A particular hierarchy that has been mounted can later be unmounted.

An OpenExtensions for z/VM Byte File System is a new type of CMS file system called a BFS (Byte File System). Byte files and traditional CMS files can be copied back and forth using the OPENVM PUT and OPENVM GET commands.

OpenExtensions for z/VM also introduces the concept of external links to the Byte File System. An external link can be thought of as a symbolic link to non-Byte File System files. It associates a CMS record file with a BFS path name. That is, an external is a file that contains the name of an object kept outside the Byte File System. Using an external link, you can associate that object with a POSIX-conforming BFS path name. If the link is to a CMS record file, you can use the path name to access the file. For example, you can create an external link to map /u/donovan/helloworld to HELLOW MODULE A.