Interactive

User Involvement

Enhanced Definition

In the mainframe context, "interactive" refers to a mode of operation where a user directly communicates with a system or application in real-time, receiving immediate responses to input. This contrasts sharply with batch processing, which executes predefined jobs without direct user intervention. It implies a dedicated, active session between a user and the system.

Key Characteristics

- Real-time Interaction: User input is processed immediately, and output is returned without significant delay, fostering a dynamic dialogue.
- Dedicated User Sessions: Typically involves a user logging into a terminal (e.g., a 3270 terminal or emulator) and maintaining an active, persistent session.
- Program-to-User Dialogue: Applications are designed to prompt users for information, validate input dynamically, and display results or status updates instantly.
- Resource Consumption: Interactive tasks consume system resources (CPU, memory, I/O) continuously during the session, requiring careful management to ensure responsiveness for all users.
- Transaction-Oriented: Often associated with online transaction processing (OLTP) systems, where individual, discrete business transactions are processed interactively.
- Terminal-Based Interface: Historically relies on character-based 3270 terminal interfaces, although modern solutions can bridge these to web or graphical user interface (GUI) front-ends.

Use Cases

- Online Transaction Processing (OLTP): Systems like CICS or IMS DB/DC for real-time customer service, banking transactions, airline reservations, or inventory management.
- Application Development and Testing: Developers using TSO/ISPF to edit source code, compile programs, submit JCL, debug applications, and manage datasets interactively.
- System Administration and Monitoring: System programmers and operators using TSO/ISPF, SDSF, or other interactive tools to monitor system performance, manage resources, and troubleshoot issues.
- Data Entry and Query: End-users interactively entering data into databases (e.g., DB2, IMS) or querying information using tools like QMF or custom-built interactive applications.
- Time-Sharing Services: Providing multiple users simultaneous access to a mainframe system for various interactive tasks, leveraging the system's processing power efficiently.

Related Concepts

Interactive processing is fundamentally distinct from batch processing, which executes predefined jobs without real-time user input. It heavily relies on Time-Sharing Option (TSO) and Interactive System Productivity Facility (ISPF) for command execution, file management, and application development. CICS and IMS DB/DC are primary environments for high-volume online interactive transaction processing, enabling thousands of concurrent users to interact with critical business applications and databases like DB2 or IMS DB.

Best Practices:

Optimize Transaction Paths: Design interactive applications (especially CICS/IMS transactions) for minimal CPU and I/O usage per transaction to ensure quick response times and high throughput.
Input Validation: Implement robust input validation at the point of entry within interactive applications to prevent errors, improve data quality, and enhance system security.
Session Management: Properly manage user sessions, including implementing timeout mechanisms for inactivity, to free up valuable system resources and enhance security.
User Interface Design: While often character-based, design clear, intuitive, and efficient 3270 screen flows within applications to minimize user errors and maximize productivity.
Resource Governance: Utilize workload managers (e.g., WLM) to prioritize interactive workloads and ensure acceptable response times, especially for critical online systems.
Security Controls: Implement strong authentication (e.g., RACF) and authorization controls to restrict access to interactive applications and data based on user roles and least privilege principles.