Which caching enhancement allows for memory-speed operations in Exadata?

The caching enhancement that enables memory-speed operations in Exadata is Columnar Smart Scan at Memory Speed. This feature is designed to take advantage of the columnar storage format used in Exadata, allowing for efficient access and processing of data directly in memory rather than fetching it from disk. By performing operations in memory, it significantly speeds up query processing times because accessing data from memory is faster than accessing it from traditional disk storage.

In addition, Columnar Smart Scan optimizes how data is read and processed by allowing queries to read only the relevant columns needed for the specific operations, further enhancing performance. This is particularly beneficial for analytic workloads where only a subset of columns is often required.

Other options, while relevant to Exadata's overall performance enhancements, do not specifically target memory-speed operations to the same extent. For instance, data compression focuses on reducing the storage footprint, dynamic query optimization pertains to improving execution plans based on current statistics and system state, and distributed caching is related to improving data availability and speed through data being cached across multiple nodes. However, none of these provide the high-speed operation capability that the Columnar Smart Scan at Memory Speed does.