CICS Interview Questions (11 - 20)
11. Can you implement a pseudo-conversational program in CICS? Also, Describe some practical examples of how the techniques are used in real-world scenarios.
Yes, a pseudo-conversational program can be implemented in CICS and is the recommended approach for building efficient CICS applications.
How it works?
- After sending a screen (EXEC CICS SEND), the program issues a RETURN, ending the task.
- CICS saves the state (typically in a COMMAREA) and restores it when the user responds.
- When the response comes back, CICS starts a new task, passing control and data to the same program.
Real-World Example Scenarios:
It is widely used in real-world systems like banking, order processing, and travel booking for efficient resource utilization and scalability.
12. What does the CICS translator do?
The CICS translator scans and converts CICS commands (like EXEC CICS) in a source program (e.g., COBOL) into standard CALL statements that can be understood by the compiler.
- Recognizes and processes CICS commands.
- Replaces them with CALL statements to CICS-supplied routines.
- Prepares the program for compilation and execution under CICS.
13. What is meant by program reentrance?
Program reentrance means a program can be safely executed by multiple tasks at the same time without interfering with each other.
Key Points -
- The program does not modify itself during execution.
- All working storage is isolated, typically in COMMAREA or dynamically allocated memory.
- Essential in CICS, as programs may be shared among tasks.
14. What is Quasi-reentrancy?
Quasi-reentrancy means a program can be interrupted and safely resumed, as long as it does not modify shared or static areas. It ensures a CICS program is task-safe, allowing it to be paused and resumed without corrupting data.
Key Points -
- Required for CICS multitasking.
- Programs must avoid using working-storage for changing data.
- Data should be passed using COMMAREA, TDQ, or TSQ.
15. What is the importance of the Resource Control Table (RCT)?
The Resource Control Table (RCT) is used in CICS-DB2 environments to define the relationship between CICS transactions and DB2 plans. It controls authorization and resource allocation for DB2 access within CICS transactions.
Describe the CICS control blocks.
CICS uses control blocks to manage internal processing and resource handling:
| Control Block | Purpose |
|---|---|
| TCT (Terminal Control Table) | Manages terminal and transaction associations. |
| PCT (Program Control Table) | Maps transaction IDs to program names. |
| PPT (Processing Program Table) | Defines programs that can be executed under CICS. |
| FCT (File Control Table) | Contains VSAM file definitions used in programs. |
| DCT (Destination Control Table) | Defines TDQs (Transient Data Queues). |
16. Which CICS service transaction is used to gain accessibility to CICS control tables?
CEDA is the service transaction used to access and manage CICS control tables and resource definitions.
Into which table is the terminal id registered?
TCT (Terminal Control Table)
17. What is the type of PPT in CICS, and what are the uses of the PPT?
PPT (Processing Program Table) is a CICS system table that defines how programs are managed and invoked, including their location, load status, and attributes.
Uses:
- Maps program names to their load modules.
- Indicates if a program is resident or dynamically loaded.
- Tracks program status (e.g., loaded, protected).
- Enables CICS to locate and invoke the correct program for execution.
18. What is the purpose of DCT?
DCT (Destination Control Table) is a CICS system table that defines and manages Transient Data Queues (TDQs).
Key Functions:
- Specifies queue names, types (intra- or extra-partition), and attributes.
- Controls how TDQs are created, accessed, and processed.
- Enables programs to use WRITEQ TD and READQ TD commands.
19. What is a CICS map and how is it used in screen handling?
A CICS map is a screen layout definition created using BMS (Basic Mapping Support) macros. It defines how data is displayed and received from a terminal screen.
A CICS map is used to define and manage screen layouts. It allows programs to send and receive data from terminals, enabling user interaction in online CICS applications.
20. What is a mapset?
A mapset is a collection of one or more BMS maps used to define screen layouts for terminal interaction in CICS. It is a group of maps used in CICS for screen handling, allowing data to be sent to and received from terminals.