Introduction to the new mainframe Chapter 4 a

Introduction to the new mainframe Chapter 4 a: z/OS Overview © Copyright IBM Corp. , 2008. All rights reserved. Slide Animation

Introduction to the new mainframe Chapter 4 a objectives Be able to: • Give examples of how z/OS differs from a single-user operating system. • List the major types of storage used by z/OS. • Explain the concept of virtual storage and its use in z/OS. • State the relationship between pages, frames, and slots. • List several defining characteristics of the z/OS operating system. • List several software products used with z/OS to provide a complete system. • Describe several differences and similarities between the z/OS and UNIX operating systems. © Copyright IBM Corp. , 2008. All rights reserved. 2

Introduction to the new mainframe Key terms in this chapter address space addressability auxiliary storage dynamic address translation (DAT) frame input/output (I/O) middleware multiprocessing multiprogramming page / paging page data set program product real storage slot swap data set UNIX virtual storage z/OS © Copyright IBM Corp. , 2008. All rights reserved. 3

Introduction to the new mainframe What is z/OS? • The most widely used mainframe operating system • 64 -bit operating system (tri-modal addressing) • Ideally suited for processing large workloads for many concurrent users • Designed for: Ø Ø Serving 1000 s of users concurrently I/O intensive computing* Processing very large workloads Running mission critical applications securely © Copyright IBM Corp. , 2008. All rights reserved. 4

Introduction to the new mainframe Hardware resources managed by z/OS © Copyright IBM Corp. , 2008. All rights reserved. 5

Introduction to the new mainframe The Virtual Partitioning Environment q z/OS runs as one of many Operating Systems on the mainframe q Different versions of z/OS can run in different LPARs as separate runtime environments or servers q The System Programmer uses the Hardware Management Console (HMC) to elect which operating system is configured into each logical partition q Each Logical Partition is managed by the hypervisor called Processor Resource Systems Manager (PR/SM) * Logical Partition z/OS © Copyright IBM Corp. , 2008. All rights reserved. 6

Introduction to the new mainframe Partitioning allows for different runtime environments • Each LPAR contains a configuration of processors, storage and I/O • Each LPAR can run a different OS and version level • Each LPAR is assigned a processor weight Processor Resource / System Manager 15 – 60 LPARs z. VM z/OS VSE v 4. 4 V 1. 7 V 3. 1 L I N U X VSE z/OS V 3. 2 V 1. 6 V 1. 8 *** z/OS VSE V 1. 7 V 1. 5 V 3. 2 L I N U X © Copyright IBM Corp. , 2008. All rights reserved. L I N U X z. VM z/OS v 4. 2 V 1. 8 7

Introduction to the new mainframe Dedicated – Shared Logical CPs Processor Resource / System Manager cp cp cp z. VM z/OS VSE v 4. 4 V 1. 9 V 3. 1 cp cp L I N U X cp cp VSE z/OS V 3. 2 V 1. 6 V 1. 8 cp *** cp cp cp z/OS VSE V 1. 7 V 16 V 3. 2 cp cp cp L I N U X cp cp z. VM z/OS v 4. 2 V 1. 8 cp = Dedicated cp = Shared (pooled) © Copyright IBM Corp. , 2008. All rights reserved. 8

Introduction to the new mainframe Application Modules, System Programs (Macros), System Components Source Code Source Code Source Code Source Code Application LOAD Modules System LOAD Modules © Copyright IBM Corp. , 2008. All rights reserved. Source Code 9

Introduction to the new mainframe z/OS internal concepts and components • Comprised of modules, system programs (macros), system components • Management of physical storage: • Real storage • Auxiliary storage • Virtual storage • Techniques of multiprogramming and multiprocessing • Information about the system, resources, and tasks is contained in control blocks • Use of the program status word (PSW) © Copyright IBM Corp. , 2008. All rights reserved. 10

Introduction to the new mainframe Physical storage concepts and usage q Virtual storage is divided into 4 -kilobyte (1 -mb) pages q Frames, pages, slots are all repositories for a page of information q Transfer of pages between auxiliary storage and real storage is called paging q When a requested address is not in real storage, an interruption is signaled and the system brings the required page into real storage q Dynamic address translation (DAT) q z/OS uses tables to keep track of pages q Use of Storage Protection © Copyright IBM Corp. , 2008. All rights reserved. 11

Introduction to the new mainframe Physical storage management • Virtual storage is an “illusion” created through z/OS management of real storage and auxiliary storage through tables. • The running portions of a program are kept in real storage; the rest is kept in auxiliary storage • Range of addressable virtual storage available to a user or program or the operating system is an address space • Each user or separately running program is represented by an address space (each user gets a limited amount of private storage) © Copyright IBM Corp. , 2008. All rights reserved. 12

Introduction to the new mainframe Pages, Frames and Slots = 4 K Address © Copyright IBM Corp. , 2008. All rights reserved. 13

Introduction to the new mainframe Page Stealing z/OS tries to keep an adequate supply of available real storage frames on hand. When this supply becomes low, z/OS uses page stealing to replenish it. Pages that have not been accessed for a relatively long time are good candidates for page stealing. z/OS also uses various storage managers to keep track of all pages, frames, and slots in the system. © Copyright IBM Corp. , 2008. All rights reserved. 14

Introduction to the new mainframe Swapping is one of several methods that z/OS uses to balance the system workload and ensure that an adequate supply of available real storage frames is maintained. Swapping has the effect of moving an entire address space into, or out of, real storage: • A swapped-in address space is active, having pages in real storage frames and pages in auxiliary storage slots. • A swapped-out address space is inactive; the address space resides on auxiliary storage and cannot execute until it is swapped in. © Copyright IBM Corp. , 2008. All rights reserved. 15

Introduction to the new mainframe Transferring addresses to and from auxiliary storage Transferring frames in and out of Central Storage 4 K One page at a time (paging) A set of pages at a time (swapping) © Copyright IBM Corp. , 2008. All rights reserved. 16

Introduction to the new mainframe How processes and virtual storage works © Copyright IBM Corp. , 2008. All rights reserved. 17

Introduction to the new mainframe z/OS architecture address sizes (Tri-modal addressing) q An address size refers to the maximum number of significant bits that can represent an address. q With z/OS Architecture, three sizes of addresses are provided: - 24 -bit A 24 -bit address can accommodate a maximum of 16, 777, 216 (16 M) bytes. - 31 -bit With a 31 -bit address, 2, 147, 483, 648 (2 G) bytes can be addressed. - 64 -bit With a 64 -bit address, 8, 446, 744, 073, 709, 551, 616 (16 E) bytes can be addressed. q 64 – bit addressing places us in the exabyte address range (An exabyte is slightly more than one billion gigabytes) 128 x the previous addressing range of 24 bit 8 Billion x the previous addressing range of 31 bit © Copyright IBM Corp. , 2008. All rights reserved. 18

Introduction to the new mainframe The Address Space Concepts - Architecture q An Address Space provides a unique expansion through virtualization Authorized Program Call Pgm A Pgm B Memory 2 GB 2 GB Pgm C Memory (Data In Virtual –DIV) © Copyright IBM Corp. , 2008. All rights reserved. 19

Introduction to the new mainframe The address space concept 1. Each address space, called a 64 -bit address space, is 16 exabytes (EB) in size; an exabyte is slightly more than one billion gigabytes. The new address space has logically 264 addresses. The number is 16 with 18 zeros after it: 16, 000, 000 bytes, or 16 EB (see the slide). 2. The potential size is 16 exabytes because z/OS, by default, continues to create address spaces with a size of 2 GB. The address space exceeds this limit only if a program running in it allocates virtual storage above the 2 GB address. If so, the z/OS operating system increases the storage available to the user from 2 GB to 16 EB. 3. The 16 MB address became the dividing point between the two previous architectures (24 -bit addressability introduced with MVS/370 and the 31 -bit addressing introduced in the operating system MVS Extended Architecture © Copyright IBM Corp. , 2008. All rights reserved. or MVS/XA), and is commonly called the line. 20

Introduction to the new mainframe Horizontal Scaling using Data Spaces Programs can use data spaces and hiperspaces to: q Obtain more virtual storage than a single address space gives a user. q Isolate data from other tasks in the address space. Data in an address space is accessible to all programs executing in that address space. You might want to move some data to a Data Space for security restricting access to data in those spaces to certain units of work q Share data among programs that are executing in the same address space or different address spaces. - Use this space as a way to separate your data logically by its own use. Pgm A Pgm B q Provide an area in which to map a Memory data-in-virtual (DIV) object. 2 GB 2 GB Pgm C Memory (Data In Virtual –DIV) © Copyright IBM Corp. , 2008. All rights reserved. 21

Introduction to the new mainframe Cross Memory is an evolution of Virtual Storage q Dual address space or cross-memory (XM) is an evolution of virtual storage having three objectives: 1. Move data synchronously between virtual addresses located in distinct address spaces. 2. Pass the control synchronously between instructions located in distinct address spaces. 3. Execute one instruction located in one address space and its operands are located in other address space. Pgm A Pgm B Memory 2 GB 2 GB Pgm C Memory (Data In Virtual –DIV) © Copyright IBM Corp. , 2008. All rights reserved. 22

Introduction to the new mainframe What’s in an address space? q z/OS provides each user with a unique runtime container and maintains the distinction between the programs and data belonging to each address space. q Because it maps all of the available addresses, however, an address space includes system code and data as well as user code and data. Thus, not all of the mapped addresses are available for user code and data. Meta Data System Code Temp Work Areas Application Code Virtual Storage components composing an address space = Address Space Control Block (ASCB) OS Code © Copyright IBM Corp. , 2008. All rights reserved. 23

Introduction to the new mainframe Address Space Concepts – Common Storage q The z/OS design is a Share-Everything Architecture q Each Address Space uses Common Storage to share code, data and objects q The runtime size of a user address space is controlled by JCL or System Routines Runtime Container 2 GB BAR Extended Private * 16 MB Line OS Code Private PSA Common Storage * Full Function Address Spaces © Copyright IBM Corp. , 2008. All rights reserved. 24

Introduction to the new mainframe Address Space Concepts PSW – (Program Status Word) USER DATA ONLY 2**31 – 2**32 Starts at 4 GB © Copyright IBM Corp. , 2008. All rights reserved. 25

Introduction to the new mainframe Address Space Data Transfer using Bits-Bytes 4096 bytes / 8 bits sign z/OS LPAR Packaging of byte transfer 16 EB digit 512 = bytes 11000110 = C 6 4 K-byte BLOCK 0 7 1 1 0 0 0 1 1 0 8 -bits (1 byte) = word 0 64 -bit word (8 bytes) © Copyright IBM Corp. , 2008. All rights reserved. 26

Introduction to the new mainframe Address Space Concept – Module Location © Copyright IBM Corp. , 2008. All rights reserved. 27

Introduction to the new mainframe Address Space Concepts – RMODE/AMODE © Copyright IBM Corp. , 2008. All rights reserved. 28

Introduction to the new mainframe Processes and Tasks q. Two types of processes - Task Control Block (TCB) used as an access token* to track units of work - Service Request Block (SRB) used as an access token to track system services Global SRBs (inter address space) first NOTE: These have a dispatch hierarchy q Process Local SRBs (intra address space) second TCBs (intra address space) third States - ACTIVE, when its program is executing on a CP - READY, when being delayed due to CP availability - WAIT, when delayed by any reason other than a CP q Process Attributes - State - Resources - Priority - Accounting - Addressing - Security * In z/OS an address space is represented by a control block (ASCB) © Copyright IBM Corp. , 2008. All rights reserved. 29

Introduction to the new mainframe Levels of Tasks in a Job Step q All of the tasks in the job step compete independently for processor time q Tasks are performed and terminated asynchronously q There is communication between tasks under the same job step q Subtask termination begins with the lowest task and works upward Job Task TASK A 1 TASK B TASK A 2 TASK B 1 TASK A 2 a TASK B 1 a © Copyright IBM Corp. , 2008. All rights reserved. 30

Introduction to the new mainframe Program Status Word and Addressing Mode q Program execution is tracked by a CPU using a Program Status Word (PSW) q The PSW will note which addressing scheme is used in bits 31 -32 q Programs execute in the first 2 GBs of an address space in 24 bit or 31 bit mode q Above the 2 GB boundary is known as the “BAR” used for data only, no code. PSW 0 16 EB AMODE 24 = 00 AMODE 31 = 10 AMODE 64 = 11 127 (8 Billion x larger than 2 GB) “The BAR” 64 -Bit ADDRESSES (128 x larger than 16 MBs) “The LINE” Common Storage straddles the 16 MB LINE and is used by all address spaces 2 GB 24 -bit ADDRESSES 31 -BIT ADDRESSES V=R Only 24 -bit © Copyright IBM Corp. , 2008. All rights reserved. 31

Introduction to the new mainframe Storage Protection • Access Control (KKKK) – 4 bits • Fetch bit (F), controlled by z/OS to create READ protection • Reference bit ®, ON if the FRAME was read or altered by CP/Channel • Change bit ©, ON if the FRAME was altered by CP or Channel PSW Key KEY Central Storage 0 1 1 8 8 7 8 8 0 … 8 2 Frame Frame Frame 0 1 2 3 4 5 6 7 Storage KKK KFRC… © Copyright IBM Corp. , 2008. All rights reserved. 32

Introduction to the new mainframe z/OS address space types q z/OS and its related subsystems require address spaces of their own to provide a functioning operating system: -System address spaces are started after initialization of the master scheduler. These address spaces perform functions for all the other types of address spaces that start in z/OS - Subsystem address spaces for major system functions and middleware products such as DB 2, CICS, and IMS -TSO/E address spaces are created for every user who logs on to z/OS - Batch Job address spaces that runs on z/OS. © Copyright IBM Corp. , 2008. All rights reserved. 33

Introduction to the new mainframe Multi-Programming/Processing: Terminology q Commit and Roll back q Multiprocessing PGM CP Single copy CP of App Pgm q Multiprogramming PGM “””” “” “”” PGM “”” “”” q Multitasking q Thread Program q Reentrancy © Copyright IBM Corp. , 2008. All rights reserved. 34

Introduction to the new mainframe Address Space Implementation (Region) Terminal Owning Region 1 TOR Terminal Owning Region 2 TOR Application Owning Region 3 Application Owning Region 2 Application Owning Region 1 Controller Region File Owning Region FOR AOR Deploym’t Agent Region System Services Database Services Servant Region 3 Controller Region (CR) Servant Region 2 Servant Region 1 Daemon Region Lock Mgr. Region L P A R (MRO - Multi Region Operation) Deploym’t Manager Region Database Recovery Region (DBRC) Message Processing Region Message (MPP) Processing Region 1 (MPP) Lock Mgr. Services Distrib. Database Services Stored Procedures Services (SR) © Copyright IBM Corp. , 2008. All rights reserved. 35

Introduction to the new mainframe Running Multiple Instances of Products across z/OS Servers LPAR “A” LPAR “B” “A” – “B” T O R T O R AOR FOR AOR DM DM Manager Agent Region Controller Region (CR) Daemon Region DM DM Manager Agent Region AOR FOR AOR Controller Region (CR) Daemon Region DM DM Manager Agent Region AOR AOR FOR Controller Region (CR) Daemon Region LPAR “C” “B” – “C” Servant Region 3 Servant Region 2 Servant Region 1 (SR) Stored System Database Procedures Services Services Stored Procedures Services Lock Mgr. Distrib. Services Database Services Stored System Database Procedures Services Stored Procedures Services Lock Mgr. Distrib. Services Database Services © Copyright IBM Corp. , 2008. All rights reserved. S Y S P L E X 36

Introduction to the new mainframe Running Multiple Mixed Instances of Products across z/OS Servers LPAR “A” T O R LPAR “B” DM DM Manager Agent Region AOR FOR AOR Controller Region (CR) Daemon Region DM DM Manager Agent Region Controller Region (CR) Daemon Region Servant Region 3 Servant Region 2 Servant Region 1 (SR) Stored System Database Procedures Services Stored Procedures Services Lock Mgr. Distrib. Services Database Services T O R LPAR “C ” Servant Region 3 Servant Region 2 Servant Region 1 (SR) AOR Stored System Database Procedures Services Stored Procedures Services Lock Mgr. Distrib. Services Database Services T O R FOR AOR Stored System Database Procedures Services Stored Procedures Services Lock Mgr. Distrib. Services Database Services T O R AOR FOR AOR DM DM Manager Agent Region Controller Region (CR) Daemon Region © Copyright IBM Corp. , 2008. All rights reserved. Servant Region 3 Servant Region 2 Servant Region 1 (SR) 37

Introduction to the new mainframe WLM - Basics SLA The idea of z/OS Workload Manager is to create a contract between the users of the applications and the z/OS Operating System Starting point for workload control process ! SIE © Copyright IBM Corp. , 2008. All rights reserved. 38

Introduction to the new mainframe Why z/OS Workload Management (WLM) q. The design of z/OS implements a share everything architecture q z/OS runs heterogeneous workloads competing for the same resources q Each workload type requires different levels of services q Workloads are integrated with many different subsystems q On-Demand Computing requires immediate resource availability q Many products and subsystems offer different tuning externals q Provides workload distribution and routing among multiples LPARs q It’s a problem solver providing dynamic and automatic on-going tuning 8 © Copyright IBM Corp. , 2008. All rights reserved. 39

Introduction to the new mainframe WLM - A Service Class service class is used to describe a group of work within a workload having equivalent performance characteristics containing similar resource service demand. A Service Classes Service Classes NOTE there are three system-provided Service Classes automatically defined in a WLM policy: SYSTEM: Used as the default Service Class for certain system address spaces. It doesn’t have a goal and it is assigned fixed DP=255. SYSSTC: The default Service Class for system tasks and privileged address spaces. It doesn’t have a goal and it is assigned fixed DP=254. SYSOTHER: As default Service Class for non-STC address spaces when no classification rules exists for the subsystem type. It is assigned a discretionary goal. DP = Dispatch Priority © Copyright IBM Corp. , 2008. All rights reserved. 40

Introduction to the new mainframe Workload Management Concepts On. Line Processing Data Base Processing Batch Reporting SYSPLEX Batch File Updating Data Mining Transaction type: Policy Based Web "buy" vs "browse" B 2 B ƒ Batch payroll ƒ Test User/user type: Top 100 clients Typical clients ƒ Executive ƒ Design team Time periods: 8 AM – 5 PM Mon - Fri ƒ Weekends ƒ End of quarter ƒ ƒ ƒ Policy Based © Copyright IBM Corp. , 2008. All rights reserved. 08: 00 through 17: 00 41

Introduction to the new mainframe Workload Management Concepts On. Line Processing Data Base Processing Batch Reporting SYSPLEX Batch File Updating Data Mining Policy Based 17: 01 through 23: 59 Policy Based © Copyright IBM Corp. , 2008. All rights reserved. 42

Introduction to the new mainframe Workload Management Concepts On. Line Processing On. Line Shutdown Data Base Processing Batch Reporting SYSPLEX Batch File Updating Data Mining Policy Based 00: 00 Through 07: 59 Policy Based © Copyright IBM Corp. , 2008. All rights reserved. 43

Introduction to the new mainframe IRD - LPAR CPU Weight Management More Workload Demand ! pu LPAR Cluster pu pu pu Websphere (SOA) 50 weight 70 Weight pu pu Traditional OLTP Batch pu Move resources to 20 weightis … 30 weight where workload 20 Weight LPAR 2 LPAR 3 10 Weight LPAR 1 Intelligent Resource Director Processor Resource / System Manager (PR/SM) System z 10 Linux can participate if non-IFL © Copyright IBM Corp. , 2008. All rights reserved. 44

Introduction to the new mainframe IRD - Dynamic Channel Management Example OLTP Disk SOA Disk IRD modifies channel distribution to meet changing workload Director/Switch Channel Subsystem pu pu pu Websphere (SOA) pu pu pu Traditional OLTP Weight 50 == 70 LPAR 3 pu pu Batch Weight 30 = 20 Weight LPAR 2 LPAR 1 = 10 20 = Intelligent Resource Director Processor Resource / System Manager (PR/SM) System z 9 © Copyright IBM Corp. , 2008. All rights reserved. 45

Introduction to the new mainframe IRD – Channel System Priority Queuing q I/O Priority Queuing prioritizes - I/O within an LPAR - Channel Subsystem Priority - Queuing prioritizes I/O within an LPAR cluster q Allows better channel resource management - High priority work is given preferential access to the channel - Can reduce channel requirements - Managed within System z server q This feature works with the special engine native to the mainframe called the System Assist Processor (SAP) - SAP uses Work Queues for prioritizing Directing Resources through Priority © Copyright IBM Corp. , 2008. All rights reserved. 46

Introduction to the new mainframe Program products for z/OS A z/OS system usually contains additional program products (priced software) that are needed to create a practical working system: • security manager • database manager • compilers • utility programs • vendor products © Copyright IBM Corp. , 2008. All rights reserved. 47

Introduction to the new mainframe Middleware for z/OS Middleware is typically something between the operating system and an end user or end-user applications. Middleware supplies major functions not provided by the operating system. Typical z/OS middleware includes: • • • Database systems Web servers Message queuing and routing functions Transaction managers Java virtual machines XML processing functions © Copyright IBM Corp. , 2008. All rights reserved. 48

Introduction to the new mainframe Defining characteristics of z/OS • Uses address spaces to ensure isolation of private areas • Ensures data integrity, regardless of how large the user population might be. • Can process a large number of concurrent batch jobs, with automatic workload balancing • Allows security to be incorporated into applications, resources, and user profiles. • Allows multiple communications subsystems at the same time • Provides extensive recovery, making unplanned system restarts very rare. • Can manage mixed workloads • Can manage large I/O configurations of 1000 s of disk drives, automated tape libraries, large printers, networks of terminals, etc. • Can be controlled from one or more operator terminals, or from application programming interfaces (APIs) that allow automation of routine operator functions. © Copyright IBM Corp. , 2008. All rights reserved. 49

Introduction to the new mainframe Summary • • z/OS, the most widely used mainframe operating system, is ideally suited for processing large workloads for many concurrent users. Virtual storage is an illusion created by the architecture, in that the system seems to have more storage than it really has. • Each user of z/OS gets an address space containing the same range of storage addresses. • z/OS is structured around address spaces, which are ranges of addresses in virtual storage. • Production systems usually include add-on products for middleware and other functions. © Copyright IBM Corp. , 2008. All rights reserved. 50