The Table Clustered Pre-Fetch icon indicates that the pages required for the table probe operation will be requested synchronously in the background prior to the actual table probe operation being performed. The system attempts to manage the paging for the table probe to maintain that all of the pages of data necessary to perform the table probe operation stay resident within main memory until they are processed. The amount of pre-fetch paging that is performed by this data access method is dynamically controlled by the system based upon memory consumption and the rate at which rows continue to be processed.
Additionally this data access method will interrogate the row numbers for the table probe operation to determine if adjacent rows exist on the same page of data or if the system should expand the size of the I/O request to cut down on the total number of pages that will be required.