A multi-tasking hierarchical file system for VM/CMS using virtual machine communication

A UNIX-like multiuser file system is designed for VM/CMS. A tree structured hierarchical file system, with protection of each file, multi-tasking and concurrency control is implemented. The multiuser file system consists of at least two virtual machines. One, called the file server, owns all the files, handles all the commands, controls the concurrency and supports multi-tasking. The other virtual machines support the user interface in the form of CMS commands. The system allows many users to send commands simultaneously to the file server. Communication between the file server and the user utilizes the Virtual Machine Communication Facility (VMCF) software, provided in the VM Control Program (CP). The multiuser file system multi-threads the commands, so that the processing of the next command can start before the previous command gets completed. Two modes of file server operation are available. One mode, quiesce mode, notifies the user if the file server is being used by another process. The other mode, queuing mode, places the commands in the queue and services them in a multi-tasking fashion.