Why Multi-load doesn't support USI (Unique Secondary Index) instead of NUSI (Non-Unique Secondary Index)?

Why Multi-load doesn't support USI (Unique Secondary Index) instead of

1.	Why Multi-load doesn't support USI (Unique Secondary Index) instead of NUSI (Non-Unique Secondary Index)?
Answer» Teradata allows all AMP (ACCESS Module Processors) to OPERATE independently. With USI, the index subtable would have to be PRESENT on multiple AMPs, which would require COMMUNICATION between AMPs. But with NUSI, the index subtable would be present on the same AMP as the data row, which would allow that AMP to be handled independently. This is why NUSI is SUPPORTED by multi-load.