MODES OF DATABASE MIRRORING


High safety with a witness operating mode

The Transaction safety setting is full

The Records are transferred synchronously. The clients does not get a transaction committed response until the mirror server has acknowledged the principal server.

Both the quorum and the witness server are required and present.

The failover is automatic, and manual failover is also possible.

No committed transactions are lost during failover.

High Safety without a witness operating mode

The Transaction safety setting is full.

The Records are transferred synchronously. The clients does not get a transaction committed response until the mirror server has acknowledged the principal server.

The quorum is not required. The witness server is not present.

Manual failover.

No committed transactions are lost during failover.

High-performance operating mode

The Transaction safety setting is off.

The Records are transferred asynchronously. The clients gets a transaction committed response as soon as the principal server has written the transaction to the log. The principal server does not wait for acknowledgement from the mirror server.

Both the quorum and witness server are not present.

Manual failover.

Some transactions are lost during failover.

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