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Introduction to CICS. Contents. Introduction History Compatibility Typical Usage Components of CICS CICS Structure – Domains CICS Management Functions Defining Resources to CICS – Control Tables. Introduction. CICS: Customer Information Control System Product from IBM - PowerPoint PPT Presentation
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Introduction to CICS
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Contents
Introduction History Compatibility Typical Usage Components of CICS CICS Structure – Domains CICS Management Functions Defining Resources to CICS – Control Tables
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Introduction
CICS: Customer Information Control System
Product from IBM
Its principal function is to control multiple terminal users and enable them to access their files using a set of programs.
Its interface between Application Program and the Operating System.
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Introduction (Cont..)
It’s a OLTP System
It’s a Database/ Data Communication (DB/DC) system.
It’s a Terminal Control Program/ Terminal Monitor
Acts as a Application/ Transaction Server
E.g. Banks ATM programs Customer Information System, Student Registration System etc.
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History
Developed by IBM CICS developers in Hursley, England
pronounced "KIX" or "KICKS”
More than 30 years old. 90% of Fortune 500 companies use CICS.
Initially, IBM introduced CICS for small and medium mainframe systems with, perhaps, a maximum of 50 terminals. Larger sites would use IMS/DC.
As CICS has evolved, the maximum number of terminals has grown to many thousands.
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Compatibility
MVS, OS/390, z/OS VSE AIX HP OS/2 Apple Macintosh
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Typical Usage
Message Switching
Batch Job Submission
Date Entry Transactions
Inquiry Transactions
Inquiry with Update Transactions
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Message SwitchingTypical Usage
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Batch Job SubmissionTypical Usage
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Date Entry TransactionsTypical Usage
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Date Entry TransactionsTypical Usage
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Inquiry TransactionsTypical Usage
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Inquiry TransactionsTypical Usage
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Inquiry with Update TransactionsTypical Usage
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Components of CICS
Data Communication Functions
Data Handling Functions
Application Program Services
System Services
Monitoring Functions
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Data Communication Functions
This component provides an interface between CICS and terminals.
It acts as an interface to telecommunication access methods like VTAM, TCAM, BTAM.
It frees the application programs from terminal hardware through Basic Mapping Support (BMS) thus providing device and format independence.
It provides Multi Region Operations (MRO) through which more than one CICS region in a system can communicate.
Provides Inter System Communication (ISC), through which a CICS region in a system can communicate with other CICS regions systems or other non-CICS regions in other systems or other non-CICS systems.
Components of CICS
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Data-Handling Functions
Provides an interface between CICS and data.
Interface with data access methods such as VSAM and BDAM.
Interface with database access methods like DB/2, SQL/DS and DL/I
Maintain data integrity by controlling simultaneous updates, providing data recovery facilities.
Components of CICS
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Application Program Services
Provides an interface between CICS and Application programs.
Interface with COBOL, PL/1, and assembler programs.
Provides command level translation.
Provides Execution Diagnostic Facility (EDF), Command Interpreter, (CECI), Screen Definition Facility (SDF), Trace and Dump facilities.
Components of CICS
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System Services
Provides an interface between CICS and operation system and carries out functions like loading and releasing of application programs, acquiring and freeing of storage, task scheduling.
Components of CICS
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Monitoring Functions
Provides the function for monitoring the various events within CICS and the necessary statistics for system fine tuning.
Components of CICS
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CICS Structure - Domains
CICS functions are performed by Domains
The domains replace the management modules used by old versions of CICS.
Each domain has a two-character identifier.
When a user requests CICS services, the different components are invoked as required.
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CICS Structure – Important Domains
KE kernel - the main CICS control structure
DS dispatcher domain DM domain manager
domain DU dump domain GC global catalog domain LC local catalog domain LM lock domain ME message domain MN monitoring domain
PA parameter domain ST statistics domain. SI systems initialization
domain SM storage domain TI timer domain TR trace domain XM transaction manager
domain XS security domain AP application domain:
everything else in CICS
• You will see these codes in messages: DFHSM0115
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CICS Management Functions
Terminal ManagementMost CICS applications start when an end user enters data from a terminal. Terminal Management allows your applications to send or receive messages.
Security Management You can restrict access to transaction and resources.
Task ManagementCICS provides its own multi-user or multi-thread environment.
Program ManagementA typical CICS system supports many different user application programs. Loading and accessing these programs is controlled by this management function.
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CICS Management Functions (cont..)
File ManagementSome applications use non-database files. File Management provides access to VSAM and direct access (BDAM) data sets.
Queue ManagementSome applications have the requirement to store data into a queue for later retrieval. CICS supports two methods of queuing.
Recovery ManagementYou may ask CICS to protect selected resources, in the event of unexpected termination of the transaction or the system.
System Services* Storage Management
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CICS Management Functions (cont..)
System Services
* Storage Management: Acquiring storage when CICS transactions needs it.
* Time Management: A service that allows CICS transaction to request that certain actions be performed at a certain time of day, or after an elapsed period of time.
* Trace Management: A service that can be very helpful in problem determination.
* Application Program Interface (API): A ‘layer’ between application programs and CICS management functions.
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CICS Management Functions (cont..)
System Services
* Storage Management: Acquiring storage when CICS transactions needs it.
* Time Management: A service that allows CICS transaction to request that certain actions be performed at a certain time of day, or after an elapsed period of time.
* Trace Management: A service that can be very helpful in problem determination.
* Application Program Interface (API): A ‘layer’ between application programs and CICS management functions.
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CICS Management Functions (cont..)
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CICS Management Functions (cont..)
System Services
* Storage Management: Acquiring storage when CICS transactions needs it.
* Time Management: A service that allows CICS transaction to request that certain actions be performed at a certain time of day, or after an elapsed period of time.
* Trace Management: A service that can be very helpful in problem determination.
* Application Program Interface (API): A ‘layer’ between application programs and CICS management functions.
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CICS Management Functions (cont..)
System Services
* Storage Management: Acquiring storage when CICS transactions needs it.
* Time Management: A service that allows CICS transaction to request that certain actions be performed at a certain time of day, or after an elapsed period of time.
* Trace Management: A service that can be very helpful in problem determination.
* Application Program Interface (API): A ‘layer’ between application programs and CICS management functions.
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Defining Resources to CICS – Control Tables
You must define resources such as files to CICS, before you can use them.
CICS Control Program and Tables:
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Control Tables – PCT
Program Control Table (PCT)
The primary function of the PCT is to register the control information of all CICS transactions.
PCT contains a list of valid Trans-id paired with the name of a program CICS will load when the transaction is initiated with that transaction identifier.
It identifies priority and security level (RSLC) of transaction.
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Control Tables - PPT
Processing Program Table (PPT)
The Primary function of PPT is to register all CICS application programs and BMS mapsets.
The PPT keeps track of which applications are loaded on the CICS address Space (storage).
CICS uses this information to determine whether new copy of the program need to be loaded from Disk or it exists on storage.
It contains information such as Location in memory, Library address of the disk and language being used.
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Control Tables – PCT & PPT
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Control Tables - FCT
File Control Table (FCT)
The Primary function of FCT is to register the control information of all files, which are used under CICS.
FCT contains the name and type of each file and in addition lists the file control operations that are valid for each file.
It lists whether the existing records can be read sequentially or randomly, deleted or modified.
