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Overview

Overview. Offspring of S/390 operating system Same reliability, performance, scalability, and cost efficiency OS/390 geared more towards e-business and client/server interaction Allows greater flexibility Allows companies to customize their system

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Overview

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  1. Overview • Offspring of S/390 operating system • Same reliability, performance, scalability, and cost efficiency • OS/390 geared more towards e-business and client/server interaction • Allows greater flexibility • Allows companies to customize their system • Various elements that can be added to base OS

  2. Customizing the System • BDT File –To-File- allows users from one OS/390 system to copy data from another OS/390 system • C/C++ with or without Debug Tool • IBM Communications Server SecurityLevel 3- highest level of security for a TCP/IP network environment, supporting packet filtering, tunnels and NAT • OCFS Security Level 3- working with Cryptographic services (base element), provides weak and strong software cryptographic services, along with various data libraries

  3. Real World Use • 90% of the world’s largest corporations run OS/390 as central OS • Running on Hitachi, Fujitsu, IBM S/390 and Amdahl hardware • Close to 1,400 Independent Software Vendors take advantage of OS/390 • PeopleSoft, Lotus Domino, SAP R/3

  4. Scheduling • JES- Job Entry System • Before and after running the program • BAP- Base Control Program • During processing

  5. Scheduling - JES • HASP- Houston Automatic Spooling Priority • JES2 – Single processor • JES3 – Multi processor • JCL – Job Control Language

  6. Scheduling - JES

  7. Software and Hardware • The OS/390 is intimately tied to its hardware • The hardware and the software often evolved in tandem • Any discussion of OS/390 processor modes inevitably becomes a discussion of S/390 processor configuration and availability

  8. Processor Performance • Despite its limited market the OS/390 is relatively unchallenged in the area of high-end mainframe number crunching • Size, power and security make it useful for mission-critical systems like finance-oriented transaction systems • Some supporters claim that up to 90% of all high-end business data is held on an S/390 system • Such a claim is questionable; IBM has seen a decline in S/390 revenue in the past ten years with the increase of “simpler and smaller” UNIX and Windows NT solutions

  9. A Well-Endowed Machine • There is still no doubt that the S/390 systems offer serious high-end computing power. • Two kinds of processor upgrades: vertical and horizontal • Horizontal: replacing the current processor with a different one designed for that system • Vertical: adding new processors to the system • One measure of vertical growth efficiency is its “linear scalability.” • S/390 systems have near-perfect linear scalability. • Ideal for multiprocessing

  10. A Short Processor History • OS/390 evolved from first OS/360 system • First developed in 1964 by Gene Amdahl, Gerry Blaauw and Fred Brooks at IBM • Originally a uniprocessor, single-batch system • Some highlights: • 1968: first two-way SMP concurrent batch system ever • 1983: the 3084 system featured the first four-way SMP architecture. • 1999: the S/390 featured twelve-way SMP architecture with cryptographic coprocessor • Up to 32 may be clustered into a Sysplex • 2000: the vSeries 900 was released with 16-way SMP and 64-bit addressing

  11. Interesting Processor Features • System can be divided into logical partitions using Processor Resource / System Manager (PR/SM) • Each partition can feature different installations and restrict user access • Double Operation Execution • Each operation is executed twice, in parallel • The results are compared and upon mismatch the operation is performed again • CPUs feature Cryptographic Facility • Special instructions that support identification and key management • Improves security by a factor of 19 when compared to software generation of 512 bit RSA keys

  12. Memory Management • In the OS/390 there are three levels of memory managed by the operating system: • central storage • expanded storage • page data sets on disk

  13. Memory Management • Central storage manages itself based on the most recently used algorithm and workload priority • The Real Storage Manager allocates storage on the basis of demand by assigning frames from an available frame queue, also known as AFQ

  14. Memory Management • OS/390 implemented the idea of expanded storage to accommodate inactive pages • Expanded storage is addressable only as pages and is not accessible to the I/O subsystem or normal CPU instructions

  15. Memory Management • Pages with low priority or not recently used are paged out to expanded memory. • Block Paging - Pages that need to be paged out are grouped together and written out as a block in one I/O. • More efficient than normal paging in its use of I/O

  16. File Management • The OS/390 file management system uses a heirarchical approach • Features included in the system: • Directory support • Current directory and home support • Absolute and relative path names • Hard links and symbolic links • Extended attribute support • Save and restore support

  17. File Management • The OS/390 heirarchical file system views the entire file heirarchy as a collection of heirarchical file system data sets • The data set is the fundamental unit of data management in OS/390

  18. Process Management • The job as a whole is usually thought of a as a single transaction with a single purpose. • There is a specific language for the definition of such jobs, namely Job Control Language.

  19. Process Management • For every job submitted OS/390 needs to know: • Where to find the appropriate input • How to process that input • What to do with the resulting output

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