Group Control System
| Company type | Operating system |
|---|---|
| Industry | Computer software |
| Founder | IBM |
| Products | Operating system for VM environment |
| Parent | IBM |
Group Control System (GCS) is an operating system created by IBM to operate as a guest within the VM environment. Since the release of VM/SP 4, GCS has been included in IBM's System product lineup, encompassing VM/XA SP, VM/ESA, and the current z/VM, although VM/SP itself has been discontinued.
Overview
GCS establishes a platform for executing selected OS/MVS-based applications and networking middleware inside VM by emulating essential OS/MVS APIs. Unlike the standard VM guest, CMS, which provides limited OS simulation, GCS delivers the comprehensive functionality required by applications such as VTAM.
The system facilitates OS multitasking and supports workload balancing among multiple virtual machines via a group mechanism that allows communication between group participants.
Core components of GCS implementation include:
- Writable shared memory segments
- Communication through IUCV among virtual machines
- A dedicated recovery virtual machine designed to release locks in shared segments if a virtual machine terminates unexpectedly
GCS is tailored for specialized use and is not designed to serve as a general-purpose user operating system like CMS; it does not offer features such as file editing.
Prominent software operating on GCS comprises:
- VM/VTAM: IBM’s implementation of the VTAM protocol stack for VM
- RSCS: Remote Spooling Communication Subsystem, leveraging SNA resources alongside VM/VTAM to interface with other SNA/NJE systems
- NETVIEW: A network management and monitoring tool