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CICS Overview Session
Citation preview
Asias Largest Global Software & Services Company
Ver 2.0
Customer Information Control
System (CICS)
Day 1 Session 1
Updated in Nov 2004
Asias Largest Global Software & Services Company
Ver 2.0
Course Objectives
After completing this course you should be able to
Appreciate the salient features of CICS as a Transaction Processing system and as a DB/DC System
Create user interfaces using CICS Basic Mapping Support (BMS).
Access and modify VSAM files, database tables.
Handle normal and abnormal CICS exception conditions.
Use advanced features of CICS: Data Tables, Intercommunication, etc.
Asias Largest Global Software & Services Company
Ver 2.0
Sessions Outline
CICS Overview
CICS - Application Programming Considerations
CICS - Screen Handling - Basic Mapping Support
CICS - Error and Exception Handling
CICS - File and Database Handling
CICS - Program Control
CICS - Queuing Facility
CICS - Interval &Task Control
CICS - Testing and Debugging
Asias Largest Global Software & Services Company
Ver 2.0
Sessions Outline Advanced Topics
CICS - Storage Control
CICS - CICS Intercommunication
CICS - Restart and Recovery
CICS - Administration and Set-up
DB2-CICS - Case Study
Asias Largest Global Software & Services Company
Ver 2.0
CICS - Overview
Session 1
Asias Largest Global Software & Services Company
Ver 2.0
Session 1 : Objectives
To Understand the Business requirements for an online transaction processing
environment
Features and Strengths of CICS
CICS Interface and Languages available to access CICS
CICS Concepts and Terminologies
Transaction Flow
Asias Largest Global Software & Services Company
Ver 2.0
Batch System Online System
Batch System
Online System
Transaction file
MASTER FILE
REPORTS VSAM / DATABASE
Terminals
Batch and Online System
Asias Largest Global Software & Services Company
Ver 2.0
An Online System
ONLINE processing allows a user to interact with a
computer and access its resources via a terminal
Example : Railway Reservation system
Sales Processing system
Costing system
Stock Clearing System
Asias Largest Global Software & Services Company
Ver 2.0
What is CICS ?
Stands for Customer Information Control System
A world-class transaction processing system - by IBM in 1960s
Availability Four versions in OS/390, CICS Transaction server 2.1 in z/OS
AS/400, RISC/6000 & OS/2
PC Servers
Provides an interface between application programs and operating system services, such as data access and communication access
Asias Largest Global Software & Services Company
Ver 2.0
CICS Interface
Asias Largest Global Software & Services Company
Ver 2.0
CICS Concepts CICS runs as a batch job and can handle hundreds of interactive users
that are using a variety of applications
More than one CICS system (or region) can run on the same computer at the same time.
Programs running in one region do not interfere with programs running in another region
Asias Largest Global Software & Services Company
Ver 2.0
Transactions and Tasks
CICS locates a application program using a four character code called Transaction-identifier
Application programs are associated with a transaction which when invoked starts a Task
A task is the execution of an application program for a specific user
Several users may invoke the same transaction, with each given a separate task
Asias Largest Global Software & Services Company
Ver 2.0
Transactions and Tasks
TASK 1 TASK 2
TXNA TXNA
working
storage for
task 1
working
storage for
task 2
TASK 1 started at terminal1 by user1
executes TXNA.
TASK 2 started at terminal2 by user2
executes the same TXNA.
These two tasks use the same load
module associated with TXNA.
However, the working storage for
each task is different.
Asias Largest Global Software & Services Company
Ver 2.0
Features and Strengths of CICS
Multitasking within a single address space provided by the Operating System
Multithreading allowing one copy of program loaded and shared by all users
Reentrancy of programs providing separate copy of working storage for each Task
Quasi-re-entrant
Priority handling
Asias Largest Global Software & Services Company
Ver 2.0
CICS User Interfaces
Majority of CICS applications written for 3270 display terminals or PCs that are emulating 3270 terminals
Presentation and Business logic provided by CICS
the user interface is implemented using Basic Mapping Support (BMS)
CICS can also be used with other types of user interfaces CICS at the back-end provides business logic
Front end provides presentation logic
A VB program
A front-end program written in another platform
Web applications run in a Web browser through HTTP
Asias Largest Global Software & Services Company
Ver 2.0
CICS Programming Languages
COBOL Most used in mainframe
Assembler language Fairly popular till 1970s
PL/I Alternative to COBOL in 1970s & 1980s
C and C++ Object oriented classes can be developed that access CICS services
Java Newest language for writing CICS applications
Object oriented classes can be developed that access CICS services
Asias Largest Global Software & Services Company
Ver 2.0
System services
Monitoring functions
Application program
services
CICS System
Operating System ( MVS/ESA) Database
Access
Method (DL/I,
DB2)
Data
Access
(VSAM/
BDAM )
Telecommunication
Access method
(VTAM,TCAM,BTAM)
CICS/MVS
Data
handling
functions
Data
Storage Data communication
functions
CICS APP PROGRAMS (Cobol, PL/I, Assembler)
Terminal
Other systems
Asias Largest Global Software & Services Company
Ver 2.0
CICS - Terms and Definitions
Logical Unit of Work (LUW)
Synchronization Point (Syncpoint)
Basic Mapping Support
Transaction Types
Asias Largest Global Software & Services Company
Ver 2.0
Logical Unit of Work (LUW)
From the application designer's point of view, a LUW is a
sequence of actions that needs to be completed before any of
the individual actions can be regarded as complete as shown
below
- - - - - - - - - - - - - - - LUW - - - - - - - - - - - - - - -
Task A |----------------|---------------------|---------------------------
SOT Update Delete EOT
File - 1 2 records (SP)
Asias Largest Global Software & Services Company
Ver 2.0
Synchronization Point (Synchpoint)
CICS automatically issues a SYNCPOINT at the end of
each task
All the updates made by the task so far will be committed
All the resources maintained by the dynamic log will be
released
Asias Largest Global Software & Services Company
Ver 2.0
BMS
Interface between the application program and the terminal control (3270 devices)
Consists of supplied BMS modules and user-defined screen maps
Provides format independence which simplifies positioning of data on terminal
Uses maps as requested by the application program to control the formatting of terminal I/O data
Maps created using the online tool SDF/CICS
Asias Largest Global Software & Services Company
Ver 2.0
CICS Application Pgm Communication
Asias Largest Global Software & Services Company
Ver 2.0
Transaction Types
Conversational Program
Program (transaction) remains idle when waiting for
user response
Program, data areas, control blocks remain in main
storage resulting in high virtual storage utilization
Pseudo-conversational Program
Program ends after it sends data to a terminal
Program is in storage only when processing data,
otherwise storage released for other transactions/tasks.
Asias Largest Global Software & Services Company
Ver 2.0
Transaction Types (Contd.)
Non-Conversational Program Programs (transactions) that are executed without user
intervention
Examples : Automatic Task Initiator, Batch Jobs
Asias Largest Global Software & Services Company
Ver 2.0
CICS Sample Screen Customer
Inquiry
Asias Largest Global Software & Services Company
Ver 2.0
Structure Chart of a Customer
Inquiry Program
Asias Largest Global Software & Services Company
Ver 2.0
Conversation Type - Illustration
EXEC CICS SEND
SEND MAP(map_name) MAPSET(mapset_name)
FROM(data_area)
END_EXEC.
IF CONVERSATION-TYPE = CONVERSATIONAL THEN
EXEC CICS RECEIVE
MAP(map_name) MAPSET(mapset_name)
INTO(data_area)
END_EXEC
END-IF
EXEC CICS RETURN
TRANSID(txn_name)
END_EXEC.
Asias Largest Global Software & Services Company
Ver 2.0
CICS Transaction Flow
Asias Largest Global Software & Services Company
Ver 2.0
CICS- Control Programs and Tables
(IBM Supplied)
CIC
S
File
Control
(FCP)
Program
Control
(PCP)
Task
Control
(KCP)
Journal
Control
(JCP)
Terminal
Control
(TCP) Transient
Data
(TDP)
Temporary
Storage
(TSP)
Storage
Control
(SCP)
Asias Largest Global Software & Services Company
Ver 2.0
CICS Control Programs & Tables
(User Specified)
Terminal Control Program - TCT Task Control Program - PCT Program Control Program - PPT File Control Program - FCT Resource Control Program - RCT Journal control Program - JCT Temporary Storage Program - TST Transient Data Program - DCT Storage Control Program - SCT
Asias Largest Global Software & Services Company
Ver 2.0
Terminal Control Flow (TCT)
The Terminal Control
Table (TCT) has an entry
for each terminal
Together with Basic
Mapping Support,
terminal control provides
an application program,
the ability to communicate
with a terminal
Asias Largest Global Software & Services Company
Ver 2.0
Task Control (PCT)
Task control validates transactions by checking the Program Control Table (PCT)
Task is created after the transaction is validated
Concurrent processing of more than 1 task is possible (multitasking)
Error message is sent to the terminal by task control for an invalid transaction
Asias Largest Global Software & Services Company
Ver 2.0
Program Control (PPT)
Task Control passes control to Program Control, which keeps track of the location of every application program
The Processing Program Table (PPT) contains the program size, program source language, and other program information
Stores the program library address the first time to make subsequent loading of program faster
Asias Largest Global Software & Services Company
Ver 2.0
User Application Programs
The application program processes the input and
issues commands to request services that are
needed in performing the function of the
application
Asias Largest Global Software & Services Company
Ver 2.0
File Control and Database
The application program issues a command to retrieve a record from a VSAM file
VSAM/(B)DAM are the only files used in CICS and they should be defined in the File Control Table (FCT)
For access to relational database as DB2, define the attachment to DB2 in the Resource Control Table (RCT)
Asias Largest Global Software & Services Company
Ver 2.0
Journal Control
The Journal control facility automatically logs the changes on the system log, when an application changes record in a file
System log defined in the Journal Control Table (JCT) enables CICS to back-out changes when a task fails
Maximum of 99 journals
Asias Largest Global Software & Services Company
Ver 2.0
Trace Control
Tracing is a CICS debugging aid
CICS can write trace entries in a Trace Table (TRT)
Execute Diagnostic Facility (EDF) is another feature that enables interactive debugging
Command Interpreter (CECI) allows a programmer to enter and test CICS commands at the terminal directly
Asias Largest Global Software & Services Company
Ver 2.0
Dump Control
In case of serious error
conditions, CICS will
abend the task with a task
dump
The CICS transaction
ABEND message
contains the ABEND
code.
Asias Largest Global Software & Services Company
Ver 2.0
Temporary Storage Control
Controls storage of data in main storage or on disk for later retrieval
Records can be retrieved in the same sequence in which they are stored
Records reside in Temporary Storage Queue (TSQ) unless deleted or when CICS closes
Temporary Storage Table (TST) is required for recovery purpose
Asias Largest Global Software & Services Company
Ver 2.0
Transient Data control
CICS queuing function sequential queue
The Destination Control Table (DCT) contains the queue definitions
Transient data has 2 types of queue: Intra-partition transient data
Extra-partition transient data
Asias Largest Global Software & Services Company
Ver 2.0
Ending the transaction
Output of a CICS process Program extracts necessary fields from the VSAM record and setup
an output area to be sent to the terminal
Task ends when the application program issues the RETURN command
All storage associated will be released
Other tasks can use the storage just released
Asias Largest Global Software & Services Company
Ver 2.0
Starting a TASK
TXN1 Trans. Program TXC1 MAPPGC1
TXC2 MAPPGC2
TXN1 TXNPGM1
TXN2 TXNPGM2
PCT
Program. Location
MAPPGC1 In Storage
MAPPGC2 On Disk
TXNPGM1 In Storage
TXNPGM2 On Disk
PPT
Load Module Library
MAPPGC1 MAPLIB
MAPPGC2 MAPLIB
TXNPGM1 PGMLIB
TXNPGM2 PGMLIB
CICS Address Space
TXNPGM1
MAPPGC1
Asias Largest Global Software & Services Company
Ver 2.0
CICS System Responsibilities
Systems Programmer
Operators (Administrators) Application Programmer
IT Management
Asias Largest Global Software & Services Company
Ver 2.0
Session 1: Summary
Overview of Online transaction processing environment
CICS Terms and Definitions
Transaction, task, LUW, conversational and
pseudo-conversational style
CICS control programs and control tables
CICS System Responsibilities
Asias Largest Global Software & Services Company
Ver 2.0
References Yukihisa Kageyama, CICS Handbook, McGraw Hill Book
Co.
CICS/ESA Application Programming Guide, Ver.3, Release 2.1.
CICS/ESA Intercommunication Guide
Joseph Le Bert, CICS Made Easy, McGraw Hill International Editions, 1987
Raul Menendez and Doug Lowe, CICS for the COBOL Programmer, Part 1&2, Mike Murach & Associates, 1992