This feature provides additional memory for in-memory hash joins. It is automatically in effect for new customers who enable the in-memory feature. Existing customers that are going to upgrade to release 17.20 must contact Teradata customer support to enable this feature manually.
This feature may change the plan from In-Memory Hash Join (IMHJ) fan-out (FO) to In-Memory Dynamic Hash Join (IMDHJ). This feature may also reduce the number of fan-outs of an IMHJ because of large FO size.
Benefits
- More applicability for IMHJ. For example, more queries pick up In-Mem hash joins over other join types.
- More applicability for IMDHJ algorithms, which is the most efficient variation of IMHJ algorithms.
- Improvement in I/O for applicable queries.
- Improvement in CPU for applicable queries.
- Higher throughput (queries-per-hour) for concurrent execution.
Considerations
- This feature is disabled by default.