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IBM OS/360. Andrew Kennedy Kyle Hunter Mehdi Tabdili Chase Crabtree. System/360 Design Goals. Extend to Commercial, Scientific, and Real Time applications General method for using I/O devices that differed in data rate, access and function
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IBM OS/360 Andrew Kennedy Kyle Hunter Mehdi Tabdili Chase Crabtree
System/360 Design Goals • Extend to Commercial, Scientific, and Real Time applications • General method for using I/O devices that differed in data rate, access and function • Enable asynchronous operation of circuit, storage and input/output components with respect to each other (timesharing)
System/360 Series Overview • Noteworthy Models: • 25 ~ Small, specialized applications • 67 ~ Virtual Memory, TSS/360 CP-67 • 85 ~ Cache Memory • 3 Operating Systems: • DOS/360 • OS/360 • TSS/360
OS 360 Principal Control Program (PCP) • Almost all operating systems prior to the OS/360 ran using stacked job batch processing (Pugh et al., 1991). • A single job ran at a time until completion. • Scheduler level-1 – Allocated memory to one job at a time. • Supervisor level-1 – Initiated the execution of each job in turn.
MFT Could run a fixed number of prioritized jobs concurrently. Memory was divided into partitions. One job resided in each partition of memory. Supervisor level-2 – Supported the partitioning of memory and multiprogramming among the partitions. Scheduler level-2 – Permitted job inputting with concurrent program execution. Established a job queue, and initiated the execution of tasks according to priorities. MVT Allocated dynamic memory partitions for jobs which could grow bigger or smaller during execution. Supervisor level-3- Supported the partitioning of memory dynamically. Reallocated memory when were jobs completed. Scheduler level-2 OS/360 MFT and MVT
Time-Sharing Option (TSO) • IBM did significant work on timesharing systems in the 1960’s. Their experiments dealt with new concepts such as the virtual machine. • The Time-Sharing System (TSS) operating system was released in 1967 but because it was so expensive and many of IBM’s customers used OS/360 it was abandoned. • TSO software was released to run on OS/360 MVT.
What Was Done Right with IBM OS/360 • Each part was tested separately to make sure it was working properly. • Introduction of Multi- Programming • Job Control Language (JCL) • TSO and “Time Sharing” • Easier Input/Output operation
What Was Done Wrong with IBM OS/360 • Managerial Differences caused a long delay before its release. • Many Bugs at the time of its release • Complicated Installation process.
IBM OS 360 Deadlock Solutions • Devices, volumes, and memory are allocated in order on a per-job-step basis • When Temporary file space can cause deadlocks, operator intervenes and kills a job • Combination of Prevention and Detection/Removal
Commercially Successful • IBM’s OS/360 was very flexible in a way such that it was built to be able to handle any type of commercial or scientific task. • Ex: A specific model was built for the North America missile defense.
Economically Successful • “$5 Billion Gamble” • Within four weeks, IBM had 1,000 orders for the computers and associated peripherals. Two years later the company had amassed 9,000 orders (Goff, 1999). • They made the $5 billion back and made much more over the years.