Introduction To IBM Mainframe Systems

Objectives • Identify Basic Components Of Mainframe Processors • Identify Difference In Architecture • IBM’s z/Series Processors And Earlier Systems • Types Of I/O Devices On Mainframes • Define Tracks And Cylinder • Describe Features Of Mainframe OS: • Virtual Storage • Multiprogramming • Spooling • Batch Processing • Time Sharing. • Describe MVS, OS/390, And Z/Os © 2002 - Mike Murach & Associates, 2007 - HCC, IBM

Hardware Terms You Should Know • Central processing unit, or CPU • Cache • Channels (ESCON/FICON channels) • I/O devices • Multiprocessor systems • PR/SM • Logical partitions (LPAR’s) © 2002 - Mike Murach & Associates, 2007 - HCC, IBM

I/O Devices That Connect To Mainframe Servers • Direct access storage devices, or DASD • Tape Drives and Optical Disks • Display And Other Terminals • Printers © 2002 - Mike Murach & Associates, 2007 - HCC, IBM

A Partial Listing Of OS/390 And z/OS Services • Base Control Program (BCP or MVS) • Workload Manager (WLM) • Systems Management Services • Application Enablement Services • OS/390 UNIX System Services • Distributed computing services • Communication Server • LAN Services Network Computing Services • Network File System (NFS) • Softcopy Services © 2002 - Mike Murach & Associates, 2007 - HCC, IBM

New Features In z/OS Version 1, Release 2 • HiperSockets • TCP/IP Networking enhancements • Internet and Intranet Security enhancements • Distributed Print • New File System and C++ compiler • Intelligent Resource Director (IRD) © 2002 - Mike Murach & Associates, 2007 - HCC, IBM

Objectives • Applied objective • Assign an appropriate name to a new data set. • Knowledge objectives • Identify what an address space is. • In general terms, explain how address spaces are used to implement virtual storage and multiprogramming. • In general terms, explain how paging is used to transfer portions of an address space to and from real storage. • In general terms, explain how swapping is used to transfer entire address spaces in and out of virtual storage. • Identify the information contained in a volume label. • Describe the role of the VTOC in processing DASD data sets. • Describe the three data set organizations that aremost commonly used today: sequential, partitioned, and VSAM key-sequenced. • Distinguish between master and user catalogs. • Describe how the high-level qualifier in a data set name is commonly used. © 2002 - Mike Murach & Associates, 2007 - HCC, IBM

Objectives (2) • Knowledge objectives (Continued) • Describe unit allocation, volume allocation, and data set allocation. • List and describe the three types of open modes that can be used to open a file. • Distinguish between a job and a job step. • Identify the basic functions of the JOB, EXEC, and DD JCL statements. • Describe the basic function of a Job Entry Subsystem. • Name the five steps that are involved in processing a job. • Describe how the job class and priority affect the scheduling of a job. • Describe the four types of SYSOUT data that are produced by most jobs: the JES message log, the JCL listing, the system message log, and program output. • Describe how the output class affects the handling of SYSOUT data set. • Distinguish between system generation and system initialization. © 2002 - Mike Murach & Associates, 2007 - HCC, IBM

Figure 2-04a A Virtual Storage Address Space • Two Basic Areas • The Private Area • The Common Area. • Special Provisions For The First 16mb Of Address • Common Areas Have Two Sections. • Above The 16MB Line • Below It. • Common Area Contains • The Nucleus • Other Operating System Data. • The Private Area Contains • Data Unique To Each User’s Address Space • The Program Being Executed. © 2002 - Mike Murach & Associates, 2007 - HCC, IBM

Figure 2-06a DASD Labels Identify Files On A Volume • z/OS identifies data sets on DASD with labels. • DASD volumes contain a volume label, • The VTOC (Volume Table of Contents) contains labels calledData Set Control Blocks, or DSCBs, © 2002 - Mike Murach & Associates, 2007 - HCC, IBM

Rules For Forming Data Set Names • Length 1 to 44 characters (standard) 1 to 35 characters (generation data group; see chapter 12) Only first 17 characters are used for tape data sets • Characters Alphanumeric (A-Z, 0-9) National (@,#, and $) Period (.) • Qualifiers Data set names with more than 8 characters broken intoqualifiers 1 to 8 characters. Separate qualifiers with periods. • First character The first character of each qualifier must be a letter or national character. • Last character The last character of a data set name should not be a period. A valid data set name AR.TRANS.Y2001 © 2002 - Mike Murach & Associates, 2007 - HCC, IBM

The Three Levels Of Data Set Allocation • Level 1: Unit allocation • generic name or group name. • A generic name an IBM-supplied name indicating a device type • A group name, or esoteric name, flexible way to allocate units. • Level 2: Volume allocation • Volume serial number (vol-ser). • Non-specific volume request • Non-specific volume requests aren’t valid for existing data sets. • Level 3: Data set allocation • For new data sets, file labels are created, space allocated, and the VTOC is updated. © 2002 - Mike Murach & Associates, 2007 - HCC, IBM

Three Basic JCL Statements • JOB information that identifies the job. • EXEC Indicates the program to be executed. • DD Identifies a file to be processed. JCL statements for a job that prints a report //MM01RN JOB (36512),'R MENENDEZ',NOTIFY=MM01 //RPTRUN EXEC PGM=RPT3000 //CUSTMAST DD DSNAME=MM01.CUSTOMER.MASTER,DISP=SHR //SALESRPT DD SYSOUT=A //ERRLIST DD SYSOUT=A © 2002 - Mike Murach & Associates, 2007 - HCC, IBM

Figure 2-13b How JES2 and JES3 process jobs • How a job enters the system • Entering JCL commands into a display terminal. • Terminal user issues: • SUBMIT, or SUB, command • JES2 or JES3 then copies it to the queue on the JES spool. • Scheduling for execution • JES examines jobs in the queue and prioritizes the work. • Job class and priority classify a job’s importance. • An initiator program runs in the system region of an address space eligible for batch job processing. • Each initiator can handle one job at a time. © 2002 - Mike Murach & Associates, 2007 - HCC, IBM

Job Classes • Typical job class assignments • Job class Characteristics • A Execute within 15 minutes of submission. • B Execute within 30 minutes of submission. • C Execute within 1 hour of submission. • D Execute overnight. • H Hold until released by an operator. • L Execute within 15 minutes of submission • Each step is limited to 1 minute of execution time. • How job classes are assigned to initiators • Initiator Eligible job classes • 1 A • 2 B,C,D,H,L • 3 B,C • 4 C © 2002 - Mike Murach & Associates, 2007 - HCC, IBM

OUTPUT Controls • The SYSOUT data sets produced by most jobs • SYSOUT data set Description • JESMSGLG A listing of messages produced by JES2 or JES3 as the job was executed. • JESJCL The JES JCL listing is a listing of the JCL processed by the job. • JESYSMSG The system message log is a collection of message produced as the job was executed. • SYSOUT SYSOUT data produced by a program executed in the job. • Typical output class assignments • Output class Type of output • A Standard printer output, routed to one of the installation’s high-speed printers • B Special printer output. • X Held output that stays on the SYSOUT queue until released for printing or deleted. © 2002 - Mike Murach & Associates, 2007 - HCC, IBM

SYSGEN • System generation • System generation (sysgen) creates the system. • IBM sends or Downloads distribution libraries. • System generation selects and assembles components needed to create a working system. • Systems programmer codes special macro instructions specifying how components should be put together. • The output is a series of system libraries containing, the executable code that makes up the operating system. © 2002 - Mike Murach & Associates, 2007 - HCC, IBM

Initialization • System initialization • The process of starting a previously generated system • Immediately after sysgen • Reinitialized due to system maintenance or a system error. • Operator uses the system console to start an Initial Program Load, or IPL. • System clears its real storage • Loads the operating system from the system libraries © 2002 - Mike Murach & Associates, 2007 - HCC, IBM

Introduction To IBM Mainframe Systems