Hash access (ACCESSTYPE='H', 'HN', or 'MH')

The ACCESSTYPE column in the plan table has a value of 'H', 'HN', or 'MH', when the table being accessed is organized by hash, and hash access is used to access the data.

Hash access is efficient for queries that use equal predicates to access a single row on a table. Hash access also reduces CPU load. However the use of hash access requires additional storage space for maintenance of the hash space. If a table is organized by hash, index clustering is unavailable on that table.

When a hash access path is selected for a parallel group, parallelism is not selected for that parallel group, however DB2® might select parallelism for other parallel groups in the query.

When star join is enabled, DB2 does not use hash access for either the fact or dimension tables when a query contains a qualified star join.