Two types:

1. Asynchronous
2. Synchronous

Asynchronous

Transactions committed on primary as created and then transferred as soon as possible 1. no real impact to primary performance 2. risk of data loss in case of unplanned failure

Synchronous

Transactions are not committed on primary until acknowledged on secondary 1. Can impact primary performance 2. No risk of data loss

Because of distance between regions, its usually asynchronous.

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