7/31/2019 Ch01 Slides[1]

1/17

CICS, C1 2001, Mike Murach & Associates, Inc. Slide 1

Chapter 1

CICS conceptsand terms

7/31/2019 Ch01 Slides[1]

2/17

CICS, C1 2001, Mike Murach & Associates, Inc. Slide 2

Objectives

1. In general terms, describe what CICS does.

2. Explain how CICS functions in an OS/390 environment.

3. List the programming languages that can be used to write CICSapplications and identify the most popular one.

4. In general terms, describe what 3270 emulation software does.5. Describe at least one of the alternate user interfaces you can use to

develop the presentation logic for a program whose business logic

is written in CICS.

6. Describe the most common way a task is started under CICS.

7. Distinguish between multitasking and multithreading.8. Describe the function of the CICS API.

7/31/2019 Ch01 Slides[1]

3/17

CICS, C1 2001, Mike Murach & Associates, Inc. Slide 3

Objectives (continued)

9. Briefly describe the function of each of the following CICSservices:

terminal control interval control

basic mapping support storage control

file control task control

program control dump control

temporary storage control

10.Briefly describe the function of each of the following CICS tables:

Program Control Table

Processing Program Table

File Control Table

7/31/2019 Ch01 Slides[1]

4/17

CICS, C1 2001, Mike Murach & Associates, Inc. Slide 4

A CICS interface

CICS provides an interface between application programs andoperating system services, such as data access and communication

access.

Operating system

CICS

Data access(VSAM,DB2,IMS)

Communicationaccess

(VTAM, SNA,TCP/IP)

Disk storage

User interface

Applicationprograms

7/31/2019 Ch01 Slides[1]

5/17

CICS, C1 2001, Mike Murach & Associates, Inc. Slide 5

CICS in an OS/390 address space

More than one CICS system (or region) can run on the same

computer at the same time.

OS/390

CICS production

region

Batch

Job

CICStest

region

TSO

user

Address space 1 Address space 2 Address space 3 Address space 4

7/31/2019 Ch01 Slides[1]

6/17

CICS, C1 2001, Mike Murach & Associates, Inc. Slide 6

CICS transaction server platforms

Hardware Operating system

IBM zSeries 900 z/OS

IBM S/390 OS/390, MVS, VSE

IBM AS/400 OS/400

IBM RS/6000 AIX (UNIX)

PC server Windows NT, OS/2

7/31/2019 Ch01 Slides[1]

7/17

CICS, C1 2001, Mike Murach & Associates, Inc. Slide 7

CICS programming languagesLanguage Description

COBOL The most used programming language for both batch and online

applications in a mainframe environment.

Assembler

language

Assembler language is used mostly for special-purpose devices like ATM

machines.

PL/I You probably wont find any new program development being done inPL/I.

C and C++ Traditionally used in engineering and math environments. With C++, an

object-oriented language, you can develop object-oriented classes that

access CICS services.

Java The newest language for writing CICS applications, Java can also be used

for developing object-oriented classes that access CICS services.

7/31/2019 Ch01 Slides[1]

8/17

7/31/2019 Ch01 Slides[1]

9/17

CICS, C1 2001, Mike Murach & Associates, Inc. Slide 9

Alternate user interfaces

When CICS is used with alternate user interfaces, thefront-end programprovides the presentation logic, but the CICS application is still the back-

end program that provides the business logic.

OS/390

CICS address space

Business logicPresentation logic

Web application

PC3270 emulation

Front-endapplication

Visual Basicapplication

3270

HTTP MQ Series ECI

7/31/2019 Ch01 Slides[1]

10/17

CICS, C1 2001, Mike Murach & Associates, Inc. Slide 10

How multitasking works

A taskis the execution of an application program for a specificuser.

Within CICS, two or more tasks can execute at the same time usinga CICS feature called multitasking.

CICS handles multitasking internally, within its own address space.

CICS address space

Task 1

Order entryprogram(user 1)

Task 2

Customerinquiry

program(user 2)

Task 3

Master menuprogram(user 3)

Task 4

Customermaintenance

program(user 4)

Task 5

Order entryprogram(user 5)

7/31/2019 Ch01 Slides[1]

11/17

CICS, C1 2001, Mike Murach & Associates, Inc. Slide 11

How multithreading works

With multithreading, two or more users can access the same copyof a program at the same time. CICS accomplishes this by

providing a separate copy of working storage for each user running

the program.

CICS address space

User 1

Workingstorage

Order entry program

User 5

Workingstorage

User 1

User 5

7/31/2019 Ch01 Slides[1]

12/17

How CICS invokes an application program

DMPGM01

MMAPGM1

ORDPGM1

The user enterstrans-id ORD1

CICS locatestrans-id ORD1in the ProgramControl Table

CICS locatesprogramORDPGM1 in the

ProcessingProgram Table

CICS locates load

module ORDPGM1on disk, loads itinto memory, andstarts the task

CICS address space

DMPGM01DMPGM02MMAPGM1ORDPGM1ORDPGM2

In storageOn diskIn storageOn diskOn disk

Program Location

DMPROG

MMAPROGORDPROG

DMPGM01DMPGM02MMAPGM1ORDPGM1ORDPGM2

Library Load module

ORD1

PCT

PPT

DM01DM01MMA1ORD1ORD2

DMPGM01DMPGM02MMAPGM1ORDPGM1ORDPGM2

Transaction Program

7/31/2019 Ch01 Slides[1]

13/17

CICS, C1 2001, Mike Murach & Associates, Inc. Slide 13

How a program accesses CICS services

CICS services are available to an application program through itsApplication ProgrammingInterface, orAPI.

Datamanagementservices

CICSmanagement

services

Datacommunicationservices

ApplicationProgramming

Interface

Application

programs

CICS

OS/390

7/31/2019 Ch01 Slides[1]

14/17

7/31/2019 Ch01 Slides[1]

15/17

Three ways a program can access disk data

ApplicationProgrammingInterface

File control

CICS

Applicationprograms

VSAM

OS/390

Disk storage

DB2 IMS

SQL DL/I

7/31/2019 Ch01 Slides[1]

16/17

CICS, C1 2001, Mike Murach & Associates, Inc. Slide 16

CICS services that help manage application

programsManagement service Description

Program control Provides for calling or transferring control to other

programs.

Temporary storage control Provides for storing data outside working storage

in simple files called temporary storage queues.

Interval control Provides time-related services, including services

for getting the current date and time and scheduling

tasks for execution.

Storage control Provides for allocating main storage space outside

of working storage.

Task control Provides for temporarily suspending a task that is

monopolizing CICS resources or gaining exclusive

control of a CICS resource.

7/31/2019 Ch01 Slides[1]

17/17

CICS, C1 2001, Mike Murach & Associates, Inc. Slide 17

CICS services that help manage applicationprograms (continued)

Management service Description

Dump control Produces a transaction dump when a fatal error is

encountered during the execution of an application

program.

Trace control Maintains a trace table that indicates the sequence

of CICS operations performed.

Journal control Creates a record orjournal that can be used to

restore files in the event of a task or system failure.

Transient data control Provides a convenient way to use sequential files

called destinations to store data.