Which access method is best for processing a large number of records frequently?

The choice of indexed sequential access as the best method for processing a large number of records frequently is grounded in its efficiency and versatility. This access method combines the benefits of both sequential access and the flexibility of direct access, making it particularly suitable for handling extensive datasets that require frequent access.

Indexed sequential access maintains an index that allows quick retrieval of records while also enabling records to be processed sequentially. This dual approach means that, while it can process records in the order they are stored, it also allows for rapid look-ups based on specific criteria, minimizing the time taken to find and retrieve records compared to purely sequential methods. Consequently, for systems that involve significant data handling, such as databases or large datasets, this method is efficient because it supports both high-speed access for querying and systematic processing for record management.

In contrast, other methods like sequential access can be slow for retrieving specific records, as they require going through each record in order. Random access may be quicker for direct retrieval of individual records but lacks the efficiency of processing large amounts of data in a structured manner. Hierarchical access, while useful in certain structured data environments, doesn't offer the same level of flexibility and speed for extensive workloads as indexed sequential access does. Therefore, indexed sequential access stands out as