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Fallback Table

A fallback table is a duplicate copy of a primary table. Each fallback row in a fallback table is stored on an AMP different from the one to which the primary row hashes.

Note that the fallback copy of any row is always located on an AMP different from the AMP which holds the primary copy. This is an entry-level fault tolerance strategy.

The disadvantage of fallback is that this method doubles the storage space and the I/O (on INSERT, UPDATE, and DELETE statements) for tables.

The advantage is that data is almost never unavailable because of one down AMP. Data is fully available during an AMP or disk outage, and recovery is automatic after repairs have been made.
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