Information Systems

Disk operating systems/360
• Single task (only one program at a time)
• Simple OS, with minimum storage and CPU requirements
OS/360 for system/360
• PCP (Primary control program) ran only one task at a time
• Multiple fixed tasks – up to 15 tasks, with fixed time-slices for each task
• Partitions have to be configured before start-up
MVS (Multiple virtual storage) for system/370 (originally OS/VS2)
• Multiple variable tasks – number of tasks, and their time-slices can change dynamically
• Each user/task can have virtually al the memory of 16MB
• This concept of multiple users/tasks using the virtual memory is called MVS
• This brought in the concept of address space – area where the program runs
MVS/XA (extended architecture) for system 370/XA
• Each user/task can have virtually all the memory of 2GB
• Concept of data spaces – areas for storing huge files in memory
MVS/ESA (Enterprise system architecture) for system 370/ESA and system 390/ESA
• Uses hyperspace – data buffering to avoid file I/O
• Huge files are stored in memory, and written to disk only when not needed
Z/OS architecture is an evolutionary upgrade of 390/ESA architecture
• It is IBM’s high end server OS
• Robust IBM e-server Z-series mainframe OS for e-business
• Highly secure, scalable, high performance base to deploy
• Internet + Java technology-enabled applications