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ENTERPRISE SYSTEM CONCEPTS

(Supplementary Material for MAPLES VOL-I Handbook)

How is Mainframe different from PC’s

The differences between a PC and Mainframe are

I/O capabilities

Mainframes have a much larger I/O bandwidth than PC's have.

In addition Mainframe's have a lot of redundancy and serviceability features built in

Reliability

The Reliability of PC is unreliable in nature.

The Reliability of mainframe with its 99.99% uptime.

Size

A PC is about 18" square and maybe 8" wide.

But Mainframes are very large in size

Number of hard drives

A typical PC will have one or two hard drives

Mainframes on the other hand, can come with hundreds of hard drives.

Secondary Memory

PC will have 200 to 500 Gigabytes of hard drive space.

Mainframe will have Terabytes to Petabytes of hard disk space.

Primary Memory

PC will have 1 GB to 4 GB of RAM.

Mainframe will have Several GBs to Terabytes of RAM.

Why Mainframe?

Businesses today rely on the mainframe to:

Perform large-scale transaction processing (thousands of transactions per second)

Support thousands of users and application programs concurrently accessing numerous

resources

Manage terabytes of information in databases

Handle large-bandwidth communication

Mainframe strengths:

Reliability, availability, and serviceability

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The reliability, availability, and serviceability (or "RAS") of a computer system have always been

important factors in data processing. Ideally, RAS is a central design feature of all aspects of a

computer system, including the applications.

Security

This critical data needs to be securely managed and controlled, and, simultaneously, made

available to those users authorized to see it. The mainframe computer has extensive

capabilities to simultaneously share, but still protect, the firm's data among multiple users.

Scalability

The degree to which the IT organization can add capacity without disruption to normal business

processes or without incurring excessive overhead (nonproductive processing) is largely

determined by the scalability of the particular computing platform.

Continuing compatibility

The ability of an application to work in the system or its ability to work with other devices or

programs is called Compatibility.

Some universal facts about Mainframes

More and faster processors

More physical memory and greater memory addressing capability

Dynamic capabilities for upgrading both hardware and software

Increased automation of hardware error checking and recovery

Enhanced devices for input/output (I/O) and more and faster paths (channels) between I/O

devices and processors

More sophisticated I/O attachments, such as LAN adapters with extensive inboard processing

A greater ability to divide the resources of one machine into multiple, logically independent and

isolated systems, each running its own operating system

Advanced clustering technologies, such as Parallel Sysplex®, and the ability to share data

among multiple systems.

Hardware Organization

Sysplex Uniprocessor and Multiprocessor

A Sysplex (IBM's systems complex), introduced in 1990,as a platform for the MVS/ESA operating

system for IBM mainframe servers. The Sysplex consists of the multiple computers (the systems) that

make up the complex.

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A Sysplex is designed to be a solution for business needs involving any or all of the following: parallel

processing; online transaction processing (OLTP); very high transaction volumes; very numerous small

work units - online transactions, for example (or large work units that can be broken up into multiple

small work units); or applications running simultaneously on separate systems that must be able to

update to a single database without compromising data integrity.

A single system uniprocessor consists of a single central processor complex (CPC) - which consists of

a single central processor (CP) and all associated system hardware and software, controlled by a

single copy of the operating system.

Tightly coupled multiprocessors consist of a number of CPs added to a CPC that share central storage

and a single copy of the operating system. Work is assigned to an available CP by the operating

system and can be rerouted to another if the first CP fails. A loosely coupled configuration has multiple

CPCs (which may be tightly coupled multiprocessors) with separate storage areas, managed by more

than one copy of the operating system and connected by channel-to-channel communications.

A Sysplex is similar to a loosely coupled configuration, but differs in that it has a standard

communication mechanism (the cross-system coupling facility, or XCF) for MVS system applications

that enables communication between application programs on one or multiple computers. The Sysplex

is made up of a number of CPCs that collaborate, through specialized hardware and software, to

process a work load. This is what a large computer system does in general; a Sysplex, through XCF,

increases the number of processing units and operating systems that can be connected.

Base Sysplex

To help solve the difficulties of managing many MVS systems, IBM introduced the MVS systems

complex or Sysplex in September of 1990. The base Sysplex lays the groundwork for simplified

multisystem management through the cross-system coupling facility (XCF) component of MVS/ESA.

XCF services allow authorized applications on one system to communicate with applications on the

same system or on other systems. In a base Sysplex, CPCs connect by channel-to-channel

communications and a shared dataset to support the communication. When more than one CPC is

involved, a Sysplex Timer synchronizes the time on all systems.

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A Base Sysplex

The base Sysplex is similar to a loosely coupled configuration in that more than one CPC (possibly a

tightly coupled multiprocessor) shares DASD and is managed by more than one MVS image. A Sysplex

is different from a loosely coupled configuration because through XCF, there is a standard

communication mechanism for MVS system applications.

Parallel Sysplex

The Parallel Sysplex is a clustering architecture that has improved communication capabilities and

supports more connected CPCs and more copies of the operating system. There are several areas of

improvement over the base Sysplex. The Parallel Sysplex Coupling Facility stores crucial system

information, usually configured on a separate device. Use of the coupling facility increases the capacity

for data sharing among systems and subsystems.

The benefits of Parallel Sysplex are:

No single points of failure

Capacity and scaling

Dynamic workload balancing

Ease of use

Single system image

Compatible change and non-disruptive growth

Application compatibility

Disaster recovery

Parallel Sysplex architecture

A Parallel Sysplex is a symmetric Sysplex using multisystem data-sharing technology. This is the

mainframe’s clustering technology. It allows direct, concurrent read/write access to shared data from all

processing servers in the configuration without impacting performance or data integrity. Each LPAR can

concurrently cache shared data in the CF processor memory through hardware-assisted cluster-wide

serialization and coherency controls.

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Parallel Sysplex

Initializing the MVS system

Initial program loading (IPL) provides a manual means for causing a program to be read from a

designated device and for initiating execution of that program. When the system hardware is ready, you

can use the system console to load the system software.

During initialization of a z/OS system, the operator uses the system console, which is connected to the

processor controller or support element. From the system console, the operator initializes the system

control program during the nucleus initialization program (NIP) stage.

An Initial Program Load (IPL) is the act of loading a copy of the operating system from disk into the

CPU's central storage and executing it. Not all disks attached to a CPU will have loadable code on

them. A disk that does is generally referred to as an ―IPLable‖ disk, and more specifically as the

SYSRES volume.

How MVS handles the storage?

Processor storage overview

MVS locates all of the usable central storage that is online and available to the system, and creates a

virtual environment for the building of various system areas. The system uses a portion of both central

storage and virtual storage.

Central Storage: Central storage, also referred to as main storage, provides the system with directly

addressable, fast-access electronic storage of data. Both data and programs must be loaded into

central storage (from input devices) before they can be processed by the CPU.

The maximum central storage size is restricted by hardware and system architecture as follows:

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In the System/370™ architecture, the maximum main storage size is 16 megabytes.

From S/370™-XA architecture until ESA/390 architecture, the maximum memory size is 2 GB.

In z/Architecture the maximum central storage size is 16 exabytes.

Expanded Storage: This is a form of electronic storage addressable in 4 KB blocks through the use of

a 32-bit block number by special privileged instructions. The expanded storage was originally intended

to bridge the gap in cost and density between main storage and magnetic media; later it provided a

means to relieve the performance constraint imposed by the 31-bit real-address size by serving as a

high-speed backing store for paging and for large data buffers.

Auxiliary Storage: The auxiliary storage is in Direct Access Storage Devices (DASD) and is used to

support basic system requirements as follows:

– System data sets.

– Paging data sets, which contain the paged-out portions of all virtual storage address

spaces. In addition, output to virtual I/O devices may be stored in the paging data sets.

Multiple virtual storage

Multiple Virtual Storage, more commonly called MVS, was the most commonly us operating

system on the System/370 and System/390 IBM mainframe computers. It was developed by IBM, but is

unrelated to IBM's other mainframe operating systems, e.g., VSE,VM.

IBM added Unix support (originally called OPEN EDITION) in MVS/SP V4.3 and has obtained POSIX

and Unix certifications at several different levels.

Swapping and Paging

The paging and swapping controllers of the auxiliary storage manager attempt to maximize I/O

efficiency by incorporating a set of algorithms to distribute the I/O load as evenly as is practical. In

addition, every effort is made to keep the system operable in situations where a shortage of a specific

type of page space exists.

Addressing mode

Addressing mode (AMODE) is a program attribute to indicate which hardware addressing mode should

be active to solve an address, that is, how many bits should be used for solving addresses.

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RMODE indicates where a program should be placed in the virtual storage, when the system loads it

from DASD:

RMODE=24: Indicates that the module must reside below the 16-MB virtual storage line.

RMODE= ANY: Indicates that the module might reside anywhere in virtual storage either above

or below the 16-MB virtual storage line.

AMODE and RMODE are load module attributes and are placed in the load module’s directory entry in

the partitioned data set.

Architecture of Virtual Address space

In latest versions of Mainframes 64 bit Virtual addressing is used. The initial support for 64-bit virtual

addressing was introduced in z/OS Version 1 Release 2. The size of the 64-bit address space is 16

exabytes, which makes the new address space 8 billion times the size of the former S/390 address

space. Programs continue to be loaded and to run below the 2 gigabyte address; these programs can

use data that resides above 2 gigabytes.

z/OS V1R2 provides for up to 256 GB of central storage to be configured to a z/OS image.. The

address space is still created with a size of 2 GB. The address space only become bigger when a

program allocates virtual storage above 2GB. To allocate and release virtual storage above 2G, a

program must use the services provided in the IARV64 macro. The GETMAIN, FREEMAN, STORAGE,

and CPOOL macros do not allocate storage above the 2 gigabyte address, nor do callable cell pool

services.

User private area

The area above the bar is intended for application data; no programs run above the bar. No system

information or system control blocks exist above the bar, either. Currently there is no common area

above the bar.

Dynamic address translation

In a 16 EB address space with 64-bit virtual storage addressing, there are three additional levels of

translation tables, called Region tables. They are called region third table (R3T), region second table

(R2T), and region first table (R1T). The Region tables are 16 KB in length, and there are 2048 entries

per table. Each region has 2G bytes.

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Dataspace and Hiperspace

Data space is a type of space with a range up to 2 GB of contiguous virtual storage. The virtual storage

map of a data space is quite different; except for the first 4K, the entire 2 GB is available for user data.

A data space can hold only data; it does not contain MVS control blocks or programs in execution.

Program code does not execute in a data space, although a program can reside in a data space as

data. A program can refer to data in a data space at byte level, as it does in a work file.

A program references data in a data space directly, in much the same way it references data in an

address space. It addresses the data by the byte, manipulating, comparing, and performing arithmetic

operations. The program uses the same instructions (such as load, compare, add, nd move character)

that it would use to access data in its own address space. Before accessing data in a data space, a

program must change its access mode, meaning, use special assembler instructions to change its

access mode.

High performance data access—hiperspace—is a kind of data space created with the same RSM

services used to create a data space. Hiperspace™ provides the applications an opportunity to use

expanded storage as a substitute to I/O operations. Hiperspaces differ from data spaces in the

following ways:

Main storage is never used to back the virtual pages in hiperspace.

Data can be retrieved and stored between a hiperspace and a data space only using MVS

services. This avoids the complex programming required when accessing data in a data space.

Data is addressed and referred to as a 4K block.

Programs can use data spaces and hiperspaces to:

Obtain more virtual storage than a single address space gives a user.

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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 databases

or hiperspace for security or integrity reasons. You can restrict access to data in those spaces

to one or several units of work.

Share data among programs that are executing in the same address space or different address

spaces. Instead of keeping the shared data in common areas, create a databases or hiperspace

for the data you want your programs to share.

Provide an area in which to map a data-in-virtual object.

Input and Output devices

Input and output devices are similar in operation but perform opposite functions. It is through the use of

these devices that the computer is able to communicate with the outside world. Input data may be in

any one of three forms:

Manual inputs from a keyboard or console

Analog inputs from instruments or sensors

Inputs from a source on or in which data has previously been stored in a form intelligible to the

computer

Output information is also made available in three forms:

Displayed information: codes, numbers, words, or symbols presented on a display device like a

cathode-ray screen

Control signals: information that operates a control device, such as a lever, aileron, or actuator

Recordings: information that is stored in a machine language or human language on tapes,

disks, or printed media

Mainframe channels

A channel provides an independent data and control path between I/O devices and memory. Early

systems had up to 16 channels; the today's largest mainframe machines can have over 1000 channels.

Channels connect to control units. A control unit contains logic to work with a particular type of I/O

device. For example, a control unit for a printer would have much different internal circuitry and logic

than a control unit for a tape drive. Some control units can have multiple channel connections providing

multiple paths to the control unit and its devices.

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Control units connect to devices, such as disk drives, tape drives, communication interfaces, and so

forth. The division of circuitry and logic between a control unit and its devices is not defined, but it is

usually more economical to place most of the circuitry in the control unit.

The channels in Figure 1 are parallel channels (also known as bus and tag channels, named for the

two heavy copper cables they use). A parallel channel can be connected to a maximum of eight control

units. Most control units can be connected to multiple devices; the maximum depends on the particular

control unit, but 16 is a typical number.

Each channel, control unit, and device has an address, expressed as a hexadecimal number. The disk

drive marked with an X in Figure 1 has address 132:

The first digit is the channel number

The second digit is the control unit number

The last digit is the device number

The device address seen by software is more correctly known as a device number (although the term

address is still widely used) and is indirectly related to the control unit and device addresses.

I/O connectivity

System control and partitioning

Mainframe hardware: Logical partitions (LPARs)

Consolidation of mainframes

Protocol for Mainframe Communication

Mainframe architecture includes a variety of network capabilities. Some of these capabilities include:

IP communication among large numbers of Linux and z/OS operating systems running as z/VM

(Virtual Machine) guest machines

IP communication among independent operating systems running in logical partitions (LPARs)

on the same machine

IP communications among a tightly coupled cluster of mainframe LPARs (called a Parallel

Sysplex)

Communications via the TCP/IP suite of protocols, applications, and equipment (for example,

the Internet, intranets, and extranets)

System Network Architecture (SNA) suite of protocols and equipment, including subarea and

Advanced Peer-to-Peer Networking with high performance routing (APPN/HPR)

Integration of SNA into IP networks using Enterprise Extender (EE) technology

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z/OS Communications Server

The z/OS operating system includes a software component called z/OS Communications

Server. z/OS Communications Server implements the SNA and TCP/IP protocols.

SNA and TCP/IP on z/OS

In the past, a mainframe backbone network used SNA. With the prevalence of TCP/IP and the

introduction of SNA/IP integration technology and additional tools, current mainframe networks

are migrating to IP-based networks.

Subsystems

Logical partition

Logical partitions (LPARs) are, in practice, equivalent to separate mainframes. Each LPAR runs its own

operating system. This can be any mainframe operating system; there is no need to run z/OS®, for

example, in each LPAR. The installation planners may elect to share I/O devices across several

LPARs, but this is a local decision.

The system administrator can assign one or more system processors for the exclusive use of an LPAR.

Alternately, the administrator can allow all processors to be used on some or all LPARs. Here, the

system control functions (often known as microcode or firmware) provide a dispatcher to share the

processors among the selected LPARs. The administrator can specify a maximum number of

concurrent processors executing in each LPAR. The administrator can also provide weightings for

different LPARs; for example, specifying that LPAR1 should receive twice as much processor time as

LPAR2.

The operating system in each LPAR is IPLed separately, has its own copy of its operating system, has

its own operator console (if needed), and so forth. If the system in one LPAR crashes, there is no effect

on the other LPARs.

JES and types of JES

MVS uses a JES to receive jobs into the operating system, schedule them for processing by MVS, and

control their output processing. JES2 is descended from HASP (Houston automatic spooling priority).

HASP is defined as a computer program that provides supplementary job management, data

management, and task management functions such as scheduling, control of job flow, and spooling.

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HASP remains within JES2 as the prefix of most module names and the prefix of all messages sent by

JES2 to the operator.

JES2 is a functional extension of the HASP II program that receives jobs into the system and processes

all output data produced by the job. So, what does all that mean? Simply stated, JES2 is that

component of MVS that provides the necessary functions to get jobs into, and output out of, the MVS

system. It is designed to provide efficient spooling, scheduling, and management facilities for the MVS

operating system.

In a JES3 environment, however, one MVS image hosts a JES3 that performs centralized control over

its and the other MVS images’ functions. This JES3 is called JES3 global processor; the JES3

instances in the other MVS images are called JES3 local processors. It is from the global processor

that JES3 manages jobs and resources for the entire complex, matching jobs with available resources.

JES3 ensures that they are available before selecting the job for processing.

TSO/ISPF

TSO/E is a base element of z/OS, as it was of OS/390 and of the former MVS systems. TSO/E has

undergone continuous enhancements during its life, and it has become the primary user interface to the

OS/390 system and, now, to the z/OS system. TSO/E provides programming services that you can use

in system or application programs. These services consist of programs, macros, and CLISTs. TSO/E

services support a wide range of functions that are useful in writing system programs as well as

application programs that exploit the full-screen capabilities of TSO/E.

CLISTs, REXX execs, servers, and command processors are specific types of programs that you can

write to run in the TSO/E environment.

The Interactive System Productivity Facility/Program Development Facility (ISPF/PDF) is a set of

panels that help you manage libraries of information on the MVS system. The libraries are made up of

units called data sets that can be stored and retrieved. You can have different kinds of information in

data sets. Some examples are:

Source code

Data such as inventory records, personnel files, or a series of numbers to be processed

Load modules

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ISPF can be used in many ways. Some examples are the following:

Users can edit, browse and print data.

Data processing administrators and system programmers can use ISPF to:

Monitor and control program libraries

Communicate with MVS through TSO commands, CLISTs, or REXX EXECs

Programmers can use ISPF to develop a batch, interactive, or any other type of program

and its documentation.

Terminal users can invoke a wide range of utilities like search, compare, compilers, and

so forth.

Programmers can use ISPF services to develop dialogs

CICS

CICS is abbreviation of Customer Information Control System

On-line transaction processor

It’s a separate sub system

Completely transaction driven and map based

It’s more like a mini operating system itself

o

o Program control facilities

o DB access calls supported

IMS

IMS is abbreviation of Information Management System

Hierarchical database management system

Very old database management system

Has it’s own communication component – IMS/DC

Limited facilities

Currently SOA is been incorporated into IMS

DB2

DB2 is abbreviation of Database 2

Database has been organized as

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Tablespaces

Tables

Rows and columns

It supports referential integrity

The SQL calls can be embedded in any high level language

VTAM

VTAM is abbreviation of Virtual Telecommunication Access Method

VTAM provides a method by which application programs can communicate with

telecommunication devices and their users.

VTAM was the first IBM program to allow programmers to deal with devices as ―logical units‖

without having to understand the details of line protocols and device operation.

Prior to VTAM, programmers used IBM’s Basic Telecommunications Access Method (BTAM) to

communicate with devices that used the binary synchronous (BSC) and start-stop line protocols.

RACF

RACF is abbreviation of Resource Access Control Facility

The z/OS Security Server is the IBM security product.

The RACF product is a component of the z/OS Security Server and works together with the

existing system features of z/OS to provide improved data security for an installation.

If this product is to be installed in your environment, then RACF customization must be done.

RACF helps meet the need for security by providing:

Flexible control of access to protected resources

Protection of installation-defined resources

Ability to store information for other products

Choice of centralized or decentralized control of profiles

An ISPF panel interface

Transparency to end users

Exits for installation-written routines

Internal reader (INTRDR)

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An internal reader is a special SYSOUT data set that other programs can use to submit jobs, control

statements, and commands to JES2.

The INTRDR statement specifies the characteristics of all JES2 internal readers that are used to

submit batch jobs.

Jobs that allocate internal reader and time-sharing users use the internal readers to submit jobs

Initiator

The initiator is an integral part of z/OS that reads, interprets, and executes the JCL.

It is normally running in several address spaces (as multiple initiators).

An Initiator manages the running of batch jobs, one at a time, in the same address space.

Classes

The CLASS parameter is used to assign your job to a job processing class.

The class you should request depends on the characteristics of the job and your installation's rules

for assigning classes.

Consult your installation's operations staff or MVS System Programmer for a list of valid job classes

and their processing characteristics.

Emulator

Dumb terminals

Device which consists of a keyboard and a monitor, and a connection to a full-fledged (intelligent)

computer usually a server PC, minicomputer, or a mainframe computer. Dumb terminals have no

'intelligence' (data processing or number crunching power) and depend entirely on the computer (to

which they are connected) for computations, data storage, and retrieval. Dumb terminals are used by

airlines, banks, and other such firms for inputting data to, and recalling it from, the connected computer.

Need of Emulators

An emulator duplicates the functions of one system using a different system, so that the second

system behaves like (and appears to be) the first system. This focus on exact reproduction of external

behavior is in contrast to some other forms of computer simulation, which can concern an abstract

model of the system being simulated.

Emulators maintain the original look, feel, and behavior of the digital object, which is just

as important as the digital data itself.[6]

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Despite the original cost of developing an emulator, it may prove to be the more cost efficient

solution over time.[7]

Reduces labor hours, because rather than continuing an ongoing task of continual data

migration for every digital object, once the library of past and present operating

systems and application software is established in an emulator, these same technologies are

used for every document using those platforms.

Many emulators have already been developed and released under GNU General Public

License through the open source environment, allowing for wide scale collaboration.[8]

Emulators allow video games exclusive to one system to be played on another.

Types of Emulators

CPU simulator

I/O

Logical simulators

Functional simulators

Video game console emulators

Terminal emulators

PCOMM configuring and customizing

IBM Personal Communications is an industry-leading, traditional Windows emulator that provides

comprehensive connectivity and access to host data.

Provides an optimal platform for traditional access to data and applications on the host.

Features 3270, 5250 and VT emulation, FTP client, SNA application support, and SNA and

TCP/IP connectivity.

Supports nearly any protocol, including TN3270(e), TN5250, ISDN, HPR, and SNA, to help you

connect a user to any data, anywhere.

Offers extensive API support, including Emulator High-Level Language Applications

Programming Interface (EHLLAPI), through programming languages such as C++, VBScript,

and Java.

Provides SNA interfaces of LUA, APPC, and CPI-C on the Microsoft Windows platform.

Maintains the integrity of SNA LU6.2/CPIC/APPC applications over IP, providing the only

solution for transporting SNA applications over an IP network.

New in V6: End user conveniences including Scratch Pad, Quick Connect, Find Text, and

improved copy options

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New in V6: Support for the latest Windows versions, including Windows V7 and Windows

Server 2008

New in V6: FTP client security

Highlights

Provides market-leading host connectivity and emulation

Includes tools to easily combine host and desktop applications

Helps you capitalize on existing investments and extend applications to Web-based

technologies

Enables users to have access to mission-critical business systems

Designed for Microsoft Windows

Batch processing

Batch processing is execution of a series of programs ("jobs") on a computer without manual

intervention.

Batch jobs are set up so they can be run to completion without manual intervention, so all input data is

preselected through scripts or command-line parameters. This is in contrast to "online" or interactive

programs which prompt the user for such input. A program takes a set of data files as input, processes

the data, and produces a set of output data files. This operating environment is termed as "batch

processing" because the input data are collected into batches on files and are processed in batches by

the program.

Batch processing has these benefits:

It allows sharing of computer resources among many users and programs,

It shifts the time of job processing to when the computing resources are less busy,

It avoids idling the computing resources with minute-by-minute manual intervention and

supervision,

By keeping high overall rate of utilization, it better amortizes the cost of a computer, especially

an expensive one.

Online processing

Online transaction processing, or OLTP, refers to a class of systems that facilitate and manage

transaction-oriented applications, typically for data entry and retrieval transaction processing. The term

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is somewhat ambiguous; some understand a "transaction" in the context of computer or database

transactions, while others (such as the Transaction Processing Performance Council) define it in terms

of business or commercial.[1] OLTP has also been used to refer to processing in which the system

responds immediately to user requests. An automatic teller machine (ATM) for a bank is an example of

a commercial transaction processing application.

The technology is used in a number of industries, including banking, airlines, mail order, supermarkets,

and manufacturing. Applications include electronic banking, order processing, employee time

clock systems, e-commerce, and eTrading. The most widely used OLTP system is

probably IBM's CICS.[2]

Online Transaction Processing has two key benefits: simplicity and efficiency.

Goals of Problem analysis

The goal of problem analysis is usually to find and fix the underlying error so that the problem will not

recur. The search for the nature of the error can be narrowed to a particular S/W product, subsystem,

component, or application program. The data relevant to the problem will need to be collected and

documented

The following are the problem analysis resources:

Reference manuals

SYS1.LOGREC and EREP. MVS records errors on the SYS1.LOGREC data set to provide a

record of all H/W failures, certain S/W errors and system conditions such as IPLs.

Traces. A trace maintains a record of certain events that occur during system operation for later

analysis. System

Dumps

Slip

IBM support structure

SMP/E

What is dump?

Dumps are record of the contents of some parts of storage at some point in time. The intent of a dump

is to provide useful information for analyzing problems and failures after they have occurred.

The types of Dumps are:

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SYMPTOM DUMP.

SNAP DUMP

SYSUDUMP

SYSABEND

SYSMDUMP

SVCDUMP

STAND-ALONE

Mainframe in the corporate world

Most of the corporate database and applications resides on IBM mainframes. The hype around PC and

mid-range servers notwithstanding, these applications continue to be a very important part of corporate

computing world. The talks of these mainframes becoming extinct have not materialized yet. Reasons

are not far to seek out:

Legacy applications are robust and reliable and time tested. The average uptime of a mainframe

system is as high as 99.99% as per Gartner reports.

The total cost of ownership for a mainframe is less than equivalent cost of a mid-range server.

This takes into account not only acquiring the hardware and software initially, but also

maintaining it in the long run.

High Investment in the existing applications

Excellent Performance and ability to scale up

In fact, IBM continues to enhance and sell more mainframes.

New business model

However, IS role in business is changing dramatically, 5 years back IS was one of the many support

departments in an organization. Today IS needs to be a mirror image reflection of the organization’s

business model

Extended organizations

The organization includes its customers and vendors as part of an extended organization. The ―End

User‖ of the IT applications in this extended organization can be an employee, a vendor, an agent or a

customer himself. This end-user needs a secure and easy access from a browser to the company’s

business critical applications so that it can be accesses from anywhere.

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Continuous availability

The Mainframe availability used to be measured in 5 9’s. That is Normal Mainframe availability given by

IBM is 99.999%. The continuous availability can be achieved thru the following facilities and protocols.

TCP/IP

VTAM

Unix System Services

Support for J2EE platform etc.,

Connectors to connect existing applications

These connectors have well defined APIs.

Tools available to generate Java Classes from existing application structures.

Java based and non-java based connectors are available.

Major connectors

CICS Transaction Gateway (CTG) to connect to CICS

MQSeries to connect to Batch, CICS and IMS

CICS Web support to connect to CICS (Non-Java)

IMS Connect to connect to IMS

JDBC, SQLJ and Net. data to connect to DB2

Java has fast emerged as standard programming language for server side logic.

IBM has adopted Java for all its e-initiatives on S/390:

Most of the enterprise connectors are Java based.

CICS and IMS support Java as one of the programming languages

CICS TS 2.1 onwards supports EJB

SQL embedded Java programming is supported (SQLJ)