# Message Redelivery

Qualified messages will be redelivered in a failover situation.

- Persistent

  When a failure occurs, messages with delivery mode `PERSISTENT`, that were not successfully acknowledged before the failure, are redelivered.

- Synchronous Mode

  When using durable subscribers, EMS guarantees that a message with `PERSISTENT` delivery mode and written to a `store` with the property `mode=sync`, will not be lost during a failure.

- Delivery Succeeded

  Any messages that have been successfully acknowledged or committed are not redelivered, in compliance with the JMS specification.

- Topics

  All topic subscribers continue normal operation after a failover.

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