MVS (Day 1)

Copyright © 2005, Infosys Technologies Ltd 2 ER/CORP/CRS/OS01/003 Version No: 1.0 Objectives To introduce mainframes –Hardware and Software To introduce internals of MVS To introduce VSAM and non-VSAM data sets To introduce job management in MVS To introduce various subsystems and facilities To introduce TSO and ISPF

Copyright © 2005, Infosys Technologies Ltd 3 ER/CORP/CRS/OS01/003 Version No: 1.0 Prerequisites Knowledge about basic computer architecture Basic knowledge in Operating System concepts Knowledge about I/O and communications

Copyright © 2005, Infosys Technologies Ltd 4 ER/CORP/CRS/OS01/003 Version No: 1.0 Evaluation Strategy ComponentMarksSchedule Mock Quiz (Optional) Not Evaluated Day 3 (Day 1 and Day 2 topics) Module Test100Day 4 (All topics)

Copyright © 2005, Infosys Technologies Ltd 5 ER/CORP/CRS/OS01/003 Version No: 1.0 References 1.Robert. H. Johnson, MVS – Concepts and Facilities, McGraw-Hill Book Company, Doug Lowe, MVS JCL - Mike Murach & Associates, MVS/DFP - IBM Manual 4.Doug Lowe, MVS TSO PART1 CONCEPTS AND ISPF, Mike Murach & Associates, Jay Ranade, Hirday Ranade, VSAM Concepts, Programming, and Design - McGraw-Hill 6. IBM On-line Manuals - IGG3L100, IGG3U100 and IGG3V400. On MVS.

Copyright © 2005, Infosys Technologies Ltd 6 ER/CORP/CRS/OS01/003 Version No: 1.0 Course Plan Day 1 Introduction to Mainframes –Hardware & Software Evolution Distinguishing characteristics of a mainframe OS Basic Mainframe Architecture Address spaces Mechanisms in Multiple Virtual Storage Day 2 Data set management –Describe the organization of data sets –VSAM and Non-VSAM Job Management –How does JCL specify its processing requirements ? –Job Entry Subsystem –Phases of a job Day 3 Various subsystems & facilities most commonly found on a typical Mainframe system System generation & initialization TSO/ISPF

Copyright © 2005, Infosys Technologies Ltd 7 ER/CORP/CRS/OS01/003 Version No: 1.0 Agenda – Day1 Introduction –Comparison of computer types Personal, Mini & Mainframes –Evolution of Mainframe hardware and software –Distinguishing characteristics of a mainframe OS –Basic Mainframe architecture –I/O device structure Concepts & terminology –Idea of address spaces –Mechanisms in Multiple Virtual Storage –MVS address space organizations ( Memory maps )

Copyright © 2005, Infosys Technologies Ltd 8 ER/CORP/CRS/OS01/003 Version No: 1.0 Basic Components of Computer Systems

Copyright © 2005, Infosys Technologies Ltd 9 ER/CORP/CRS/OS01/003 Version No: 1.0 Classification of computers Personal Computer Mainframe Computer Super ComputerMini Computer

Copyright © 2005, Infosys Technologies Ltd 10 ER/CORP/CRS/OS01/003 Version No: 1.0 Personal Computers

Copyright © 2005, Infosys Technologies Ltd 11 ER/CORP/CRS/OS01/003 Version No: 1.0 Minicomputer

Copyright © 2005, Infosys Technologies Ltd 12 ER/CORP/CRS/OS01/003 Version No: 1.0 Mainframe

Copyright © 2005, Infosys Technologies Ltd 13 ER/CORP/CRS/OS01/003 Version No: 1.0 Super Computers. High Processing capacity Uses:. Scientific computations. Military applications

Copyright © 2005, Infosys Technologies Ltd 14 ER/CORP/CRS/OS01/003 Version No: 1.0 Mainframe Hardware Evolution

Copyright © 2005, Infosys Technologies Ltd 15 ER/CORP/CRS/OS01/003 Version No: 1.0 Mainframe System Software Evolution … DOS/VSE OS/360 PCP OS/MFT

Copyright © 2005, Infosys Technologies Ltd 16 ER/CORP/CRS/OS01/003 Version No: 1.0 Mainframe System Software Evolution OS/MVT OS/VS1 and SVS MVS Z/OS

Copyright © 2005, Infosys Technologies Ltd 17 ER/CORP/CRS/OS01/003 Version No: 1.0 Mainframe OS - characteristics Virtual storage Multiprogramming Spooling Batch processing Time sharing

Copyright © 2005, Infosys Technologies Ltd 18 ER/CORP/CRS/OS01/003 Version No: 1.0 Virtual storage Technique that lets a processor simulate a large amount of main storage from a smaller installed real storage. Uses disk storage as an extension of real storage. At any given moment only one program and its data need be in real storage.

Copyright © 2005, Infosys Technologies Ltd 19 ER/CORP/CRS/OS01/003 Version No: 1.0 Multiprogramming More than one program executing at the same time. Key : I/O waits take a long time compared to CPU operations. Only a simulation again.

Copyright © 2005, Infosys Technologies Ltd 20 ER/CORP/CRS/OS01/003 Version No: 1.0 Spooling Intercepts and redirects printer output to a disk file. Each programs’ output stored separately. Facilitates effective sharing of I/O devices and better system throughput.

Copyright © 2005, Infosys Technologies Ltd 21 ER/CORP/CRS/OS01/003 Version No: 1.0 Batch processing Batch processing is - –Non interactive –Off line JCL describes a batch job - programs, data and resources required. Job scheduler : submits jobs for execution based on scheduling algorithm.

Copyright © 2005, Infosys Technologies Ltd 22 ER/CORP/CRS/OS01/003 Version No: 1.0 Time sharing Time sharing makes on-line, interactive processing possible. Each user has access to the system and a gets a time slice repeatedly. TSO used to login, create, maintain and store JCLs. Processing is generally as a batch job in background.

Copyright © 2005, Infosys Technologies Ltd 23 ER/CORP/CRS/OS01/003 Version No: 1.0 Basic Mainframe architecture … A family of processors from IBM channel 0 channel 1 channel 2 channel 3 channel 4 channel 5 channel 6 channel 7 CPU Main storage Processor

Copyright © 2005, Infosys Technologies Ltd 24 ER/CORP/CRS/OS01/003 Version No: 1.0 Basic Mainframe architecture... Processor-CPUs+Main store+channels – cache – expanded storage Multiprocessing (more than one CPU) –PR/SM - Processor resource / systems manager

Copyright © 2005, Infosys Technologies Ltd 25 ER/CORP/CRS/OS01/003 Version No: 1.0 Basic Mainframe architecture... Channels - –provides a path between a processor and an I/O device. ( 4.5 MB/sec, 400-foot ) –Each channel can connect to upto 8 control units each of which is connected to an I/O device. –A channel is intelligent ( a CPU in itself ) ESCON - Enterprise System Connection - based on fiber optics ( 17 MB/sec,26 miles )

Copyright © 2005, Infosys Technologies Ltd 26 ER/CORP/CRS/OS01/003 Version No: 1.0 I/O Devices Unit record devices – card devices & printers Magnetic tape devices –sequential access only Direct access devices –disk drive, DASD, auxiliary,.secondary storage –random access possible

Copyright © 2005, Infosys Technologies Ltd 27 ER/CORP/CRS/OS01/003 Version No: 1.0 Magnetic Tapes It is one of the commonly used I/O. Coated with a magnetic material on both sides of the tape. Data is stored by Magnetizing the ferrite coating. Sequential access of records. Used for bulk storage and easy transportation.

Copyright © 2005, Infosys Technologies Ltd 28 ER/CORP/CRS/OS01/003 Version No: 1.0 Direct Access Storage Device (DASD) A DASD consists of many disk packs or volumes: Data on both sides Platters

Copyright © 2005, Infosys Technologies Ltd 29 ER/CORP/CRS/OS01/003 Version No: 1.0 DASD - Tracks & Cylinders TRACK 000 TRACK 807

Copyright © 2005, Infosys Technologies Ltd 30 ER/CORP/CRS/OS01/003 Version No: 1.0 DASD - Actuator READ-WRITE HEADS

Copyright © 2005, Infosys Technologies Ltd 31 ER/CORP/CRS/OS01/003 Version No: 1.0 DASD: Data format … There are two types of Data Formats: Fixed block data format Count Key data format (CKD format)

Copyright © 2005, Infosys Technologies Ltd 32 ER/CORP/CRS/OS01/003 Version No: 1.0 DASD - Data format CKD ( count-key-data) devices - –Store data in variable-length blocks –Each data block preceded by a count area and a key area ( which should be met before data in dir of rotation ) –Gaps to separate count, key and data areas.

Copyright © 2005, Infosys Technologies Ltd 33 ER/CORP/CRS/OS01/003 Version No: 1.0 DASD - control units … Each type of DASD requires two types of control units to connect to a channel : –String controller : attaches a group of DASDs of same type ( a string ) – Storage control : connects upto 8 DASD strings to a channel Cache between processor & drive. Support for more than one channel connection to processor.

Copyright © 2005, Infosys Technologies Ltd 34 ER/CORP/CRS/OS01/003 Version No: 1.0 DASD - Control units

Copyright © 2005, Infosys Technologies Ltd 35 ER/CORP/CRS/OS01/003 Version No: 1.0 Data communications equipment … Lets local & remote terminals access a system : –host system –communications controller –modems –telecommunication lines –terminal systems

Copyright © 2005, Infosys Technologies Ltd 36 ER/CORP/CRS/OS01/003 Version No: 1.0 Data communications equipment

Copyright © 2005, Infosys Technologies Ltd 37 ER/CORP/CRS/OS01/003 Version No: 1.0 Terminals 3270 terminals are the standard. It is a subsystem of many terminals, printers and controllers Terminals can be emulated on PCs which accesses the mainframe over wide area links.

Copyright © 2005, Infosys Technologies Ltd 38 ER/CORP/CRS/OS01/003 Version No: 1.0 Concepts & terminologies

Copyright © 2005, Infosys Technologies Ltd 39 ER/CORP/CRS/OS01/003 Version No: 1.0 Address space What is an Address Space? –An address space is a complete range of addresses that can be accessed by a processor.

Copyright © 2005, Infosys Technologies Ltd 40 ER/CORP/CRS/OS01/003 Version No: 1.0 Addressability of different Systems Depends on number of bits used for addressing : –System 370 : 24 bit addressing, 16 MB max –370 XA, ESA 370,390 : 31 bit addressing, 2GB max. –Z series – 64 bit addressing 16 EB 24 bit Addressing (MVS) 31-bit Addressing (MVS/XA) 16 MB “ Line” 2 GB “Bar” 64 bit Addressing (z/OS)

Copyright © 2005, Infosys Technologies Ltd 41 ER/CORP/CRS/OS01/003 Version No: 1.0 Multiple Virtual Storage … MVS simulates several address spaces, each independent of the other and representing an user, job or a OS subsystem. Mechanisms used to support MVS : –Paging –Swapping

Copyright © 2005, Infosys Technologies Ltd 42 ER/CORP/CRS/OS01/003 Version No: 1.0 Multiple Virtual Storage...

Copyright © 2005, Infosys Technologies Ltd 43 ER/CORP/CRS/OS01/003 Version No: 1.0 Paging … Pages are 4K sections on virtual store ( DASD ). Page frames are 4K sections in real store ( main memory ). Page table maps pages to page frames. Page fault when program refers to data in a storage location not in real store.

Copyright © 2005, Infosys Technologies Ltd 44 ER/CORP/CRS/OS01/003 Version No: 1.0 Paging Page-in when MVS loads a new page into a page frame Page-out when data in a page-frame is written back to DASD. OS code responsible for paging cannot be paged out.

Copyright © 2005, Infosys Technologies Ltd 45 ER/CORP/CRS/OS01/003 Version No: 1.0 Expanded Storage: Acts as large buffer between real storage and page data sets ( virtual store ). Improves efficiency of virtual storage operations.

Copyright © 2005, Infosys Technologies Ltd 46 ER/CORP/CRS/OS01/003 Version No: 1.0 Swapping … Transfer of entire address spaces in and out of virtual store. Swapping is like paging, only at a higher level and across address spaces.

Copyright © 2005, Infosys Technologies Ltd 47 ER/CORP/CRS/OS01/003 Version No: 1.0 Swapping

Copyright © 2005, Infosys Technologies Ltd 48 ER/CORP/CRS/OS01/003 Version No: 1.0 Program modes Real mode –not pageable or swappable –OS part responsible for implementing virtual memory, always resident Virtual mode –Other processes that can be paged or swapped

Copyright © 2005, Infosys Technologies Ltd 49 ER/CORP/CRS/OS01/003 Version No: 1.0 MVS/370-Memory map … System area –OS programs & data, common to all address spaces, nucleus, real mode Private area –User region + unallocated Common area –OS programs & data, common to all address spaces –SQA, PLPA and CSA

Copyright © 2005, Infosys Technologies Ltd 50 ER/CORP/CRS/OS01/003 Version No: 1.0 MVS/370 - Memory map...

Copyright © 2005, Infosys Technologies Ltd 51 ER/CORP/CRS/OS01/003 Version No: 1.0 MVS/370 - Memory map

Copyright © 2005, Infosys Technologies Ltd 52 ER/CORP/CRS/OS01/003 Version No: 1.0 Storage map in an Address Space System area –OS programs & data, common to all address spaces, nucleus, real mode Private area –User region + unallocated Common area –OS programs & data, common to all address spaces

Copyright © 2005, Infosys Technologies Ltd 53 ER/CORP/CRS/OS01/003 Version No: 1.0 Memory map - XA and ESA 31 bit addresses => 2 GB total First 16 MB can be addressed using either 24 or 31 bit addressing –address space logically divided at 16 MB line No system area –MVS nucleus combined with other OS data in common area

Copyright © 2005, Infosys Technologies Ltd 54 ER/CORP/CRS/OS01/003 Version No: 1.0 MVS/ESA - Dataspace ESA lets a job or user create one or more 2GB address spaces that can be used to hold large amounts of data Contents of dataspaces managed directly by user programs Dataspaces reside in normal virtual store subject to paging and swapping.

Copyright © 2005, Infosys Technologies Ltd 55 ER/CORP/CRS/OS01/003 Version No: 1.0 Difference between Address space and Data space Address space Data space Contains instruction and data. Can contain only data. Even if program is loaded in data space, it is considered as data Common areas and nucleus is mapped None of common areas and nucleus is on Address space. mapped on data space. An application can have only one An application can have access upto 7999 address space. data space, each the size of 2GB.

Copyright © 2005, Infosys Technologies Ltd 56 ER/CORP/CRS/OS01/003 Version No: 1.0 MVS/ESA - Hiperspace Similar to dataspaces Contents of hiperspaces managed by MVS/ESA and made available to user programs in 4KB units Hiperspaces reside only in expanded storage and are never in real store Facilitates hiperbatch to improve performance of certain types of batches –hiperbatch transparent to JCL that invokes them

Copyright © 2005, Infosys Technologies Ltd 57 ER/CORP/CRS/OS01/003 Version No: 1.0 Data SpaceHiperspace AccessAccess Registers MVS SystemServices Addressability Byte 4 Kb Blocks Storage Central, Expanded, Expanded, Auxiliary Auxiliary Language Assembler Assembler and Support High Level The differences between data spaces and Hiperspaces

Copyright © 2005, Infosys Technologies Ltd 58 ER/CORP/CRS/OS01/003 Version No: 1.0 Summary Introduction –Comparison of computer types Personal, Mini & Mainframes –Evolution of Mainframe hardware and software –Distinguishing characteristics of a mainframe OS –Basic Mainframe architecture –I/O device structure Concepts & terminology –Idea of address spaces –Mechanisms in Multiple Virtual Storage –MVS address space organizations ( Memory maps )

Copyright © 2005, Infosys Technologies Ltd 59 ER/CORP/CRS/OS01/003 Version No: 1.0 Thank You!