INTRODUCTION
There are two types of computer application systems. One is the batch application system and the other is the online application system. The batch system has a system environment where jobs run one by one in a conventional way, whereas the online system has the system environment where many transactions run concurrently.
The primary objective of CICS is to provide the control and services functions of the DB/DC system as a package. That way, CICS users can develop their own customized DB/DC system by concentrating on the application development based on their own needs, freed from detailed considerations for the operating system and computer hardware, including communication terminals.
CICS itself is not a DB/DC system unless applications accompany it, because CICS provides only the control environment for the DB/DC system. This is why CICS is categorized as a DB/DC control system.
Features Of CICS
CICS makes data communication much easier by supplying all the basic components needed to handle data communication. This allows system designer and programmers to concentrate on developing application programs without having to concern with the details of data transmission, buffer handling or the properties of individual terminal devices.
As far as the operating system is concerned, CICS is an application program that is it runs as a job in one of the system’s partition or region, which is a virtual address space. Therefore CICS takes part in multiprogramming environment of the operating system. CICS is a longer running job therefore it remains up during the day time collecting on- line transactions and at night batch jobs are executed for master file updation etc.
Multitasking means that the operating system (OS) allows more than one task to be executed concurrently, regardless of whether the tasks use the same program or different programs. Therefore, this is not a unique concept of CICS. But, CICS manages multitasking of CICS task within its own region. That is CICS provides a multitasking environment where more than one CICS task run concurrently.
When user requests a transaction, normally by logging on and keying in a transaction code, CICS checks the status of the user and the terminal. This ensures the validity of user, terminal and transaction-id. Then task control creates a task for the transaction. CICS tries to give the best response times to the most important or urgent work. Usually, several tasks are competing for resources, so a transaction, an operator, and a terminal are each assigned a priority related to the importance of the function they carry out. CICS sums these priorities to give the overall priority of the task and uses this priority to decide the order in which to process competing tasks. Since transactions are not normally processed through to completion in a single, uninterrupted option, CICS makes such decisions every time a task returns control to CICS.
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CHAPTER 1. BASIC CONCEPTS-CICS
CHAPTER 2. SYSTEM COMPONENTS.
CHAPTER 3. BMS MAP DESIGN
CHAPTER 4. CICS COMMANDSCHAPTER 5. CICS PROGRAMMING.
CHAPTER 6. ADDITIONAL COMPONENTS
CHAPTER 7. CONDITIONS.
CHAPTER 8. CONTROL OPERATIONS.
CHAPTER 9. FILE HANDLING.
CHAPTER 10. QUEUES.
CHAPTER 11. TRANSACTIONS.
CHAPTER 12. ABBEND CODES.
CHAPTER 13. CICS PROGRAMS.
CHAPTER 14. FAQ's ON CICS.
