When
Bulk fetch is faster than retrieving one row at a time when a large number of rows qualify for each scan of the table or index. Bulk fetch uses extra memory to hold the pre-fetched rows, so it should be avoided in situations in which memory is scarce.
Bulk fetch is automatically turned off for updatable cursors, for hash
joins, for statements in which the scan returns a single row, and for subqueries.
It is useful, however, for table scans or index range scans:
The default size for bulk fetch (16 rows) typically provides good performance.