You can define fallback protection for a simple or aggregate join index.
With fallback, you can access a join index and its base table if an AMP fails, with little impact on performance.
Without fallback, an AMP failure has significant impact on both availability and performance as follows.
- You cannot update the base table referenced by a join index even if that base table is defined with fallback.
- The Optimizer cannot access a join index on a down AMP to create query plans. Performance can be degraded significantly when this occurs.
You cannot use the NO FALLBACK option and the NO FALLBACK default on platforms optimized for fallback.
The cost of having fallback for a join index when running a DML request that modifies a base table referenced by the join index is a slight increase in processing to maintain the fallback copy of the join index.