Inquiry

Enhanced Definition

In the mainframe context, an inquiry refers to a real-time, read-only request for specific information from a database or system, typically initiated by an end-user via an interactive terminal. Its primary purpose is to retrieve and display data without modifying the underlying records, providing immediate responses to user queries.

Key Characteristics

- Read-Only Operation: Inquiries are designed exclusively for data retrieval and do not alter, add, or delete any information in the underlying data sources.
- Real-time Processing: They provide immediate responses to user requests, making them suitable for interactive applications requiring up-to-the-minute data.
- Interactive User Interface: Often driven by user input through a 3270 terminal emulator, utilizing screen maps (e.g., CICS BMS maps) for data entry and display.
- Transaction-Oriented: Frequently implemented as part of an online transaction processing (OLTP) system, such as a CICS or IMS TM transaction.
- Specific Data Retrieval: Typically targets particular records or fields based on user-provided criteria, rather than processing large data sets.
- Low Resource Footprint (per transaction): Designed for quick execution and minimal resource consumption to support high volumes of concurrent users.

Use Cases

- Customer Service: A customer service representative querying a customer's account balance, order status, or transaction history.
- Inventory Management: Checking the current stock level of a specific product in a warehouse or retail system.
- Airline Reservations: Looking up flight availability, passenger details, or booking information in real-time.
- Financial Services: Displaying a specific bank account's current status, recent transactions, or loan details.
- System Monitoring: An operator displaying the status of a particular CICS region, IMS control region, or a specific task.

Related Concepts

Inquiries are a cornerstone of Online Transaction Processing (OLTP) systems, particularly within environments like CICS and IMS Transaction Manager (IMS TM). They rely on efficient access to data stored in DB2, IMS DB, or VSAM files. An inquiry application is typically written in COBOL or PL/I, interacting with a terminal emulator through Basic Mapping Support (BMS) maps (for CICS) or Message Format Services (MFS) (for IMS TM) to present data to the user. They are distinct from batch processing, which handles large volumes of data offline.

Best Practices:

Optimize Database Access: Ensure SQL queries (for DB2) or DL/I calls (for IMS DB) are highly optimized, utilizing appropriate indexes to minimize I/O and CPU usage.
Implement Robust Error Handling: Provide clear, user-friendly messages for invalid input, data not found, or system errors to guide the user.
Design User-Friendly Interfaces: Use well-structured BMS maps or MFS formats to create intuitive screens for data entry and clear presentation of inquiry results on 3270 terminals.
Minimize Data Transfer: Retrieve only the necessary fields and records to reduce network traffic and application processing overhead, improving response times.
Enforce Security and Authorization: Implement stringent RACF or equivalent security checks to ensure users can only inquire about data they are authorized to access.
Performance Monitoring and Tuning: Regularly monitor inquiry transaction response times and resource consumption, tuning the application code, database design, and system parameters as needed to maintain optimal performance.