A hash-based scan on a data-only-locked table hashes on either the extent number or the allocation page number, rather than hashing on the page number. The choice of whether to hash on the allocation page or the extent number is a cost-based decision made by the optimizer. Both methods can reduce the cost of performing parallel queries on unpartitioned tables. Queries that choose a serial scan on an allpages-locked table may use one of the new hash-based scan methods if the table is converted to data-only locking.
