Explain fallback in Teradata.

1.	Explain fallback in Teradata.
Answer» As the name implies, the fallback feature stores the second copy of rows from a table on a different AMP, which is CALLED the Fallback AMP. In the event that ONE of the AMPs fails, the fallback rows are accessed. As a result, even if one of the AMPs fails, data can still be accessed since a fallback AMP is available. In the below diagram, you can SEE how a duplicate (fallback) copy of each row is stored in another AMPs. In AMP 0, a duplicate copy of the primary row of AMP1 (3) and AMP2 (6) is stored in fallback rows. Similarly, in AMP 1, a duplicate copy of the primary row of AMP0 (1) and AMP2 (5) is stored in the fallback row. All the AMPs stored fallback VALUES in the same way.

Answer»

As the name implies, the fallback feature stores the second copy of rows from a table on a different AMP, which is CALLED the Fallback AMP. In the event that ONE of the AMPs fails, the fallback rows are accessed. As a result, even if one of the AMPs fails, data can still be accessed since a fallback AMP is available.

In the below diagram, you can SEE how a duplicate (fallback) copy of each row is stored in another AMPs. In AMP 0, a duplicate copy of the primary row of AMP1 (3) and AMP2 (6) is stored in fallback rows. Similarly, in AMP 1, a duplicate copy of the primary row of AMP0 (1) and AMP2 (5) is stored in the fallback row. All the AMPs stored fallback VALUES in the same way.

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