# How EMS Manages Persistent Messages

JMS defines two message delivery modes, `PERSISTENT` and `NON_PERSISTENT`, and EMS defines a `RELIABLE_DELIVERY` mode.

For more information see Message Delivery Modes.

`NON_PERSISTENT` and `RELIABLE_DELIVERY` messages are never written to persistent storage. `PERSISTENT` messages are written to persistent storage when they are received by the EMS server.

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