DB2 11 for z/OS Database Administration: Certification Study Guide

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DB2 11 for z/OS Database Administration

Certification Study Guide (Exam 312)

MC Press

DB2 for z/OS Introduction

This chapter introduces the DB2 z/OS environment and its various components. Later chapters will further discuss all topics, providing additional details about each one. Topics presented here will be covered on the 312 exam in various questions. The questions at the end of this chapter provide an example of the types of questions that will be asked about different areas of DB2's environment, such as address spaces, attachment facilities, SQL, commands, and utilities.

To start this introduction, let us first get an overview of the z/OS architecture on which DB2 is built, and then examine DB2 and how it is designed and constructed to be one of the industry's leading database management systems.

z/Architecture and the z/OS Operating System

With z/OS and the IBM System z10®, System z9® 109, zSeries 890, and zSeries 990 systems, you get an architecture that provides qualities of service that are critical for e-business. As a highly secure, scalable, and open operating system, z/OS offers high performance that supports a diverse application execution environment. The tight integration that DB2 has with the System z architecture and the z/OS environment creates a synergy that allows DB2 to exploit advanced z/OS functions.

The z/OS operating system is based on 64-bit z/Architecture. The robustness of z/OS powers the most advanced features of the IBM System z10 and IBM System z9technology as well as the IBM eServer™ zSeries 990 (z990), 890 (z890), and servers, enabling management of unpredictable business workloads.

DB2 benefits tremendously from z/Architecture. The architecture of DB2 for z/OS exploits the key z/Architecture feature: 64-bit virtual addressing support. With 64-bit z/Architecture, DB2 gains an immediate scalability advantage.

The following z/Architecture features benefit DB2:

• 64-bit storage

» Increased capacity of central memory from 2 GB to 16 exabytes eliminates most storage constraints. Also, 64-bit storage allows for 16 exabytes of virtual address space, a huge step in the continuing evolution of increased virtual storage. In addition to improving DB2 performance, 64-bit storage improves availability and scalability, and it simplifies storage management.

• High-speed communication

» HiperSockets™ enable high-speed TCP/IP communication across partitions of the same System z server, for example, between Linux on System z and DB2 for z/OS.

• Dynamic workload management

» The z/OS Workload Manager (WLM) provides solutions for managing distribution, balancing workloads, and distributing resources to competing workloads. With z/OS workload management, you get the combined cooperation of various subsystems (CICS, IMS/ESA®, JES, APPC, TSO/E, z/OS UNIX System Services, DDF, DB2, LSFM, and Internet Connection Server). The Intelligent Resource Director (IRD) allows you to group logical partitions that are resident on the same physical server, and in the same sysplex, into an LPAR cluster. This gives WLM the ability to manage resources across the entire cluster of logical partitions.

• Specialty engines

» With special processors, such as the System z Integrated Information Processor (zIIP), DB2 achieves higher degrees of query parallelism and higher levels of transaction throughput. The zIIP improves resource optimization and lowers the cost of eligible workloads, enhancing the role of the mainframe as the data hub of the enterprise.

In addition to the benefits of z/Architecture, DB2 takes advantage of many other z/OS operating system features:

• High security

» For decades, z/OS and its predecessors have provided robust security. Security features deliver privacy for users, applications, and data, as well as protect the integrity and isolation of running processes. Current security functions have evolved to include comprehensive network and transaction security that operates with many other operating systems. Enhancements to the z/OS Security Server provide improved security options, such as multilevel security. The System z environment offers highly secure cryptographic functions and provides improved Secure Sockets Layer (SSL) performance.

• Open software technologies

» The z/OS operating system supports the latest open software technologies, including Enterprise JavaBeans, XML, and Unicode.

• Cluster technology

» The z/OS Parallel Sysplex provides cluster technology that achieves availability 24 hours a day, 7 days a week. Cluster technology also provides the capability for horizontal growth. Horizontal growth solves the problems of performance overheads and system management issues that you typically encounter when combining multiple machines to access the same database. With horizontal growth, more scalability can be achieved; systems can grow beyond the confines of a single machine while the database remains intact.

• Solid-state drives

» Solid-state drives (SSDs) are more reliable, consume less power, and generate less heat than traditional hard-disk drives (HDDs). SSDs can also improve the performance of online transaction processing. SSDs are especially efficient at performing random access requests, and they provide greater throughput than HDDs. Some IBM System Storage® series allow a combination of HDDs and SSDs.

• Parallel Access Volume

» IBM Enterprise Storage Server® (ESS) exploits the Parallel Access Volume (PAV) and Multiple Allegiance features of z/OS and supports up to 256 I/Os per logical disk volume. A single z/OS host can issue I/Os in parallel to the same logical volume, and different hosts can issue I/Os to a shared volume in parallel.

• HyperPAV

» HyperPAV is available on some IBM System Storage series. HyperPAV helps applications to achieve equal or greater I/O performance than the original PAV feature, but uses fewer z/OS resources.

• Adaptive multi-stream prefetching

» Adaptive multi-stream prefetching (AMP) is a sequential prefetching algorithm that resolves cache pollution and prefetch waste for a cache that multiple sequential request streams share. AMP works well to manage caches efficiently across a wide variety of workloads and cache sizes.

• Cache optimization

» DB2 code and control structures are adapted to reduce cache misses.

• MIDAW

» The System z environment also supports the Modified Indirect Data Address Word (MIDAW) facility, which improves channel utilization and throughput and can potentially reduce I/O response times.

• FICON® channels

» These channels offer significant performance benefits for transaction workloads. FICON features, such as a rapid data transfer rate (4 GB per second), also result in faster table scans and improved utility performance.

• High performance FICON

» High Performance FICON (zHPF) is a new FICON protocol and system I/O architecture that results in improvements for small block transfers to disk by using the device-independent random access method.

• System z instructions

» DB2 can take advantage of the latest System z instructions. These instructions can streamline specific processes and reduce the CPU workload.

• Increased System z10 page size

» DB2 benefits greatly from the 1 MB page size of System z10. The increased page size allows for DB2 buffer pool enhancements, which can reduce the CPU workload.

• Improved hardware compression

» Improved hardware compression has a positive impact on performance. For example, utilities that run against compressed data run faster.

DB2 for z/OS

The main operating system for IBM's most robust hardware platform, IBM System z®, is z/OS. DB2 for z/OS is the enterprise data server for System z. It manages core business data across an enterprise and supports key business applications. DB2 for z/OS supports thousands of customers and millions of users. With its 64-bit z/Architecture, the z/OS platform can provide scalable, secure processing for different types of workloads in high-performance environments. The major strengths of this environment include reliability, manageability, scalability, flexibility, availability, and security.

Applications that access DB2 resources can run within the same z/OS system in the Customer Information Control System (CICS), Information Management System (IMS), Time Sharing Option (TSO), WebSphere, stored procedure, or batch environments, or other operating systems. Attachment facilities connect DB2 to each of these environments. You can execute DB2 processes in several different address space regions within z/OS, such as CICS or IMS. DB2 z/OS provides an architecture that facilitates a 64-bit operating system, which can support many diverse applications. Applications can also access DB2 resources by using the client/server services of the DB2 distributed data facility (DDF).

DB2 for z/OS can also run in a Parallel Sysplex environment. This environment is a requirement to support DB2 data sharing. Parallel Sysplex technology provides for an environment in which several processors can share data and the DB2 subsystems can have concurrent read/write access to the data. It also offers the flexibility to add new processors for increased throughput, the ability to seamlessly route workloads away from failed processors, and the capacity to balance diverse work across multiple processors.

DB2 z/OS Environment

DB2 operates as a formal subsystem of z/OS and works efficiently with other z/OS subsystems and components. A subsystem is a secondary or subordinate system that can usually operate independently of, or asynchronously with, a controlling system. A DB2 subsystem is a distinct instance of a relational database management system (DBMS). Its software controls the creation, organization, and modification of a database and the access to the data that the database stores. The z/OS processes are separated into regions that are called address spaces.

Address Spaces

DB2 for z/OS processes execute in several different address spaces, described next.

Database Services

Address space ssnmDBM1 provides the most database-related services. Most large storage areas reside above the 2 GB bar in ssnmDBM1. With 64-bit virtual addressing to access these storage areas, DB2 can scale to extremely large sizes.

Address space DSN1DBM1 (also known asDBM1) is critical because it manages most of the activities in DB2. This is the database services address space (DSAS), also called the Advanced Database Management Facility (ADMF) address space. The following subcomponents execute in this address space:

• Buffer manager

• Data manager

• Data space manager

• Large object manager (LOBM)

• Relational data system (RDS)

• Service controller

• Stored procedures manager

• Utilities (which work with associated code in an allied address space)

The DBM1 address space uses memory for several operations in DB2. It also handles prefetch I/O under a service request block (SRB).

System Services

Address space ssnmMSTR performs a variety of system-related functions. The system services address space (SSAS), DSN1MSTR (orMSTR), is also known as the data system control facility (DSCF) address space. The following subcomponents execute in this address space:

• Agent services manager

• Distributed transaction manager

• General command processor

• Group manager

• Initialization procedures

• Instrumentation facilities

• Message generator

• Recovery log manager

• Recovery manager

• Storage manager

• Subsystem support

• System parameter manager

CPU for system-level activities, such as log archiving, is accounted for in this address space.

Distributed Data Facility

Address space ssnmDIST provides support for remote requests. DDF enables client applications running in an environment that supports Distributed Relational Database Architecture (DRDA) to access DB2 data. DDF also lets one DB2 subsystem access data on another DB2 subsystem. Other relational database servers can be accessed as long as they support DRDA. TCP/IP and Systems Network Architecture (SNA) are the supported network protocols.

DDF permits up to 150,000 distributed concurrent threads to be attached to a single DB2 subsystem at once. The following resource managers execute in the DDF services address space, DSN1DIST:

• Data communications resource manager (DCRM)

• Distributed data interchange services (DDIS)

• Distributed relational data system manager (DRDS)

• Distributed transaction manager (DTM)

Internal Resource Lock Manager

The DB2 internal resource lock manager (IRLM) is both a separate subsystem and an integral component of DB2. IRLM works with DB2 to control access to your data. Each DB2 subsystem must have its own IRLM instance. IRLM is not shared between DB2 subsystems or between DB2 and IMS subsystems. IRLM works with DB2 to serialize access to your data. DB2 requests locks from IRLM to ensure data integrity when applications, utilities, and commands attempt to access the same data. It is always recommended to run with the latest level of IRLM and to have it set at the highest priority above other address spaces. IRLM is discussed in more detail later.

WLM-Established

There can be several WLM managed address spaces for stored procedures and user-defined functions. WLM-established address spaces are handled in order of priority and are isolated from other stored procedures or user-defined functions that run in other address spaces.

User Address Spaces

The z/OS processes can run in at least one, possibly several, of the following types of user address spaces:

• TSO

• Batch

• CICS

• IMS dependent region

• IMS control region

• WebSphere

DB2 works efficiently with other z/OS subsystems and components, such as the z/OS Security Server and the zSeries Parallel Sysplex environment. DB2 utilities run in the z/OS batch or stored procedure environment. Applications that access DB2 resources can run within the same z/OS system in the CICS, IMS, TSO, WebSphere, stored procedure, or batch environments, or on other operating systems. These applications can access DB2 resources by using the client/server services of the DB2 DDF. IBM provides attachment facilities to connect DB2 to each of these environments.

DB2 and the z/OS Security Server

The z/OS Security Server prevents unauthorized system access and can protect DB2 resources, such as tables. The z/OS Security Server is sometimes referred to as RACF, which is one of its key components. To control access to your z/OS system, you can use the Resource Access Control Facility (RACF) component of the z/OS Security Server or an equivalent product.

When users begin sessions, the z/OS Security Server checks their identities to prevent unauthorized system access. The z/OS Security Server provides effective protection for DB2 data by permitting only DB2-managed access to DB2 data sets. By using the z/OS Security Server, you can directly control most authorization to DB2 objects, define authorization, or use multilevel security.

DB2 and DFSMS

To manage DB2 disk data sets, you can use the DFSMSdfp Storage Management Subsystem (SMS). Its purpose is to automate the management of physical storage by centralizing control, automating tasks, and providing interactive controls for system administrators. DFSMS can reduce user concerns about physical details of performance, space, and device management. Table spaces or indexes with data sets larger than 4 GB require DFSMS-managed data sets.

Extended partitioned data sets (PDSE), a feature of DFSMSdfp, are useful for managing stored procedures that run in a stored procedures address space. PDSE enables extent information for the load libraries to be dynamically updated, reducing the need to start and stop the stored procedures address space.

DB2 Attachment Facilities

An attachment facility provides the interface between DB2 and another environment. DB2 sessions can begin from other environments on clients such as Microsoft Windows or UNIX by using interfaces such as ODBC, JDBC, and SQLJ.

You can use several different attachment facilities, depending on the environment in which a program will execute. Only one attachment can be active within a program at any given time. Each program runs in an allied (user) address space. The program calls the DB2 attachment facility modules, which execute within the allied address space and establish communications with the DB2 address spaces.

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Excerpted from DB2 11 for z/OS Database Administration by Susan Lawson. Copyright © 2016 Susan Lawson. Excerpted by permission of MC Press.
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