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Mirroring in Oracle RAC and Data Guard

A reader asks a question about mirroring on Oracle RAC using Data Guard.

Can you give me advice on mirroring with Oracle high availability, which commits transactions in both servers (primary and secondary). In Oracle Data Guard, I have not seen anything like mirroring. Oracle RAC with mirror SAN can do it, but that is too costly.

Oracle Data Guard has different protection modes which allow for this type of requirement. We discuss this in the book starting on page 310. With Maximum Protection Mode in an Oracle Data Guard environment, we do in fact have to write transactions to both the local and at least one remote standby site before the transaction is considered committed. This is discussed on page 310 of the book. On page 311, we list the requirements for being in ‘Maximum Protection Mode’:

  • The primary database must be using the SYNC attribute to stream redo
  • The standby must have Standby Redo Logs (SRLs) configured
  • A minimum of one standby database must be available
  • A snapshot standby cannot be the only standby database when in Max Protect mode

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