Driver - Control software

Enhanced Definition

In the mainframe context, a "driver" (or control software) refers to a program or software component designed to initiate, manage, or facilitate interaction with other programs, systems, or resources. It acts as an orchestrator or an interface, often used for testing, integrating disparate systems, or enabling external access to mainframe data and services.

Key Characteristics

- Orchestration: A driver program can control the execution flow of other modules, programs, or utilities, often based on specific logic or conditions.
- Interfacing: Provides a standardized mechanism for one application or system to communicate with another, abstracting the underlying complexities.
- Testing Support: Used extensively in development to create test harnesses, providing controlled inputs to specific program modules and verifying their outputs.
- Connectivity: Enables distributed applications (e.g., Java, .NET) to access mainframe resources like DB2 databases or IMS data stores via protocols like JDBC or ODBC.
- Resource Management: Can manage the lifecycle of connections, transactions, or other resources it interacts with, ensuring proper setup and teardown.

Use Cases

- Unit and Integration Testing: A COBOL or PL/I program written specifically to call a target subroutine or module with various test data sets, simulating its operational environment.
- Distributed Data Access: A JDBC driver running on a Java application server to establish and manage connections to a DB2 for z/OS subsystem, allowing external applications to query and update mainframe data.
- Batch Process Control: A JCL job executing a custom driver program that dynamically determines which subsequent utility programs (e.g., SORT, IDCAMS, IEBGENER) to invoke or which datasets to process based on input parameters or file conditions.
- System Integration: A program acting as a "bridge" or "adapter" to facilitate data exchange or transaction processing between two different mainframe applications, potentially translating data formats or invoking specific APIs.

Related Concepts

Drivers often leverage APIs (Application Programming Interfaces) provided by the operating system or other software components to perform their functions. They can be seen as a form of middleware when they bridge client applications to server resources, such as DB2 Connect acting as a gateway for distributed clients. In testing, a driver program directly interacts with the subroutines or modules under test, simulating the calling environment. For batch processing, driver programs are executed within a JCL (Job Control Language) context, often orchestrating the execution of other utilities or application programs.

Best Practices:

Modularity and Reusability: Design driver programs, especially for testing, to be modular, parameterized, and reusable across different test scenarios or modules.
Robust Error Handling: Implement comprehensive error checking, logging, and recovery mechanisms within driver programs to diagnose issues effectively and ensure stability.
Performance Optimization: For connectivity drivers (e.g., JDBC/ODBC), optimize connection pooling, transaction management, and data retrieval strategies to minimize overhead and maximize throughput.
Security Considerations: Ensure that drivers accessing sensitive mainframe resources adhere to strict security protocols, utilizing secure authentication, authorization, and encrypted communication channels.
Version Management: Maintain strict version control for drivers and ensure compatibility with the specific versions of the systems or applications they interact with to prevent runtime issues.