Which step involves gathering runtime diagnostic information?

Gathering runtime diagnostic information is primarily accomplished through the process of logging. Logging is the act of recording various events that occur during the execution of a program or system, capturing crucial information such as errors, warnings, and informational messages. This diagnostic data is invaluable for monitoring the system's performance, troubleshooting issues, and understanding how an application behaves under different conditions.

In the context of web processing or application development, effective logging enables developers and system administrators to track the execution flow, identify bottlenecks, and analyze failures. This information can later be reviewed to understand the state of the system at the time of an issue, thus assisting in debugging and improving performance.

Alternative choices like search, discovery, and producing focus on different aspects of data handling and system operations. While search pertains to retrieving specific information from a data set, discovery often relates to identifying new patterns or relationships in data. Producing is more about generating outputs based on input data rather than capturing runtime states. Therefore, logging stands out as the definitive choice for gathering runtime diagnostic information.