Other Architectures

The types of disks and files just discussed (based on 512, 1K, 2K or 4K block sizes) are part of the Enhanced Disk Format (EDF) architecture. CMS also supports Shared File System (SFS) architecture which is used for files residing in a CMS file pool.

SFS files are represented in storage in the same way EDF files are. The significant difference is that SFS files are always formatted with 4K-byte blocks. SFS shares CMS programs and data among users. SFS supports hierarchical directories and file sharing. Data kept by a file server virtual machine is on server-owned disk space, which is shared by all owners of files in that file pool. Requests for data from a CMS user machine are sent across an APPC/VM link to the server machine. Requests can be in the form of commands, CSL routine calls, or macros.