Mvs1.0

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MVS

MVS

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Basic system/370 Architecture

IBM maintains compatibility among various systems / 370 processors by designing each with the same basic architecture.The processor consists of three main parts. • CPU • Main Storage • Data Channels

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370series Processor Architecture

CHANNELS

0 1 CPU

Main Storage

2 3 4

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Multiprocessing

• Operating two or more processors simultaneously with one MVS system • In multiprocessor systems, two or four CPUs share access to common main memory. Operating system determines how each CPU is utilized.

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Concepts of MVS

Multiple Virtual Storage (MVS) is the virtual storage operating system designed to perform the system control programming functions in large customer environments MVS is based on three important system concepts • Virtual Storage • Multiprogramming • Spooling – Managing CPU storage space

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MVS Features • Virtual storage operating system supporting uniprocessor, attached processor and coupled multiprocessor configurations. • Integrated time sharing(TSO) facilities with individual address spaces. • System resource manager for dynamic workload management. • VSAM master catalog and user catalogs. • Virtual I/O for temporary datasets. • Functional recovery routines for system components. • Job entry functions supported by standard job entry sub-systems JES2 or JES3. • Cross memory services for interaddress space communication reduces assigned common virtual storage and sub-system overhead.

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MVS Features

• Message suppression facility to allow user defined control over informational messages. • Improved online problem determination via extensions to operator command facilities. • Support for 31-bit virtual storage addresses. • Support for various add on subsystems to perform functions like file and device management. • Enhanced job management using JES2 and JES3 Job Entry Systems. • Dynamic I/O reconfiguration using DFSMS.

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MVS

Languages – FORTRAN – VS COBOL II – PL/1 – CLIST and REXX – IBM ‘C’ – ASSEMBLER 370

HARDWARE – MVS – 4341 THRU 3090 – MVS/XA – 4381 THRU 3090 – MVS/ESA – 3090 – MVS ES/9000

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Spooling

• Multiprogramming increase I/O device utilization by allowing several programs that use different I/o devices to execute at the same time. • A conflict will result when two or more programs try to access a device that can not be shared, such as a printer. • Spooling eliminates this problem by acting as an interface between programs and non-shareable devices.

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Virtual Storage Management

MVS Nucleus • Nucleus resides in the lowest area of fixed storage • Contains - most heavily used parts of the operating system and control • Function - operation of the virtual storage is not pageable

Pageable supervisor and link pack area Master Scheduler Region Dynamic Region Non-Pageable Dynamic Region MVS Nucleus CSC Proprietary 12/02/08 04:22 PM 008_fmt_blk

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Job Scheduling

Job Scheduler • Selects jobs for processing from the job queue • Starts an initiator/terminator task that allocate the device and main storage needed to run the program

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Job Entry Subsystem

• Combines the function of scheduling and spooling to provide a comprehensive facility for processing jobs through a MVS system • It is the job entry subsystem that reads and process JCL • Provides many options for the final disposition of spooled output data based on the class and device specified in the JCL.

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JES2 AND JES3

• JES2 – Is designed for single processor systems – Can handle only simple job scheduling functions

• JES3 – Is designed for large multiprocessor systems – Can handle complicated job scheduling functions

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Data management services

MVS provides automatic data management services • Data set storage control • Cataloging • Space allocation • security

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MVS subsystems

SUBSYSTEMS • TSO – ISPF – PDF

• • • • •

CICS/MVS DB2 IMS JES2 JES3

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Time sharing option (TSO)

Features • Each user has full facility of MVS • Comprehensive, easy to use edit facility • Command list facility (CLIST)- TSO command procedures • SUBMIT command to send work from foreground to background.

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Time sharing option(TSO)

Benefits • Increase in productivity • Interactive computing leads to increased efficiency • Offers the widest range of functions through the widest range of terminals to the widest range of users of any IBM interactive computing system.

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Data set Labels

Under MVS storage entity such as tape or disk is called volume • A volume may contain many files • Volume is identified by volume serial number • VTOC – For direct access volumes , a special area – Contains data set labels for each file on the volume

• Each label in VTOC gives – Data set name – Data control block information – Location of the data set on the disk

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Data Set Name

• • • • • •

Consists of one or more qualifiers Maximum of eight characters long Qualifiers are separated by periods Maximum length of data set name is 44 including periods. First qualifier is called high level qualifier First character in each level must be a letter – For Example : CSCINDIA.TRAINING.COURSES

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Data Control Block

• DCB is a table in storage used by various routines of control I/O operations • Usually DCB parameters are coded in JCL

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Data set Organization

Two methods of Data set organization • Sequential data set • Partitioned data set (PDS) – Consists of a directory and one or more members – Each member function as a sequential data set

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Commonly used ISPF Commands • Locate or L • Insert or I • Delete or D • Copy or C • Move or M • Overlay or O • Repeat or R • Shift or ( • Exclude or X • Find or F • Change or C CSC Proprietary 12/02/08 04:23 PM 008_fmt_blk

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Thanks

THANK YOU

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