Apama 10.3 | Apama Documentation | Developing Apama Applications | Developing Apama Applications in EPL | Using Correlator Persistence
Using Correlator Persistence
Description of state that can be persistent
When persistence is useful
When non-persistent monitors are useful
How the correlator persists state
Enabling correlator persistence
How the correlator recovers state
Designing applications for persistence-enabled correlators
Upgrading monitors in a persistence-enabled correlator
Sample code for persistence applications
Requesting snapshots from EPL
Developing persistence applications
Using EPL plug-ins when persistence is enabled
Using the MemoryStore when persistence is enabled
Comparison of correlator persistence with other persistence mechanisms
Restrictions on correlator persistence
When the correlator shuts down, the default behavior is that all state is lost. When you restart the correlator, no state from the previous time the correlator was running is available. You can change this default behavior by using correlator persistence.
Correlator persistence means that the correlator automatically periodically takes a snapshot of its current state and saves it on disk. When you shut down and restart that correlator, the correlator restores the most recent saved state.
To enable persistence, you indicate in your EPL code which monitors you want to be persistent. Optionally, you can write actions that the correlator executes as part of the recovery process. When code is injected for a persistence application, the correlator that the code is injected into must have been started with a persistence option.
Persistent monitors must be written in EPL. State in JMon monitors cannot be persistent. State in chunks, with a few exceptions, also cannot be persistent.
To protect the security of personal data, see Handling personal data "at rest" in the correlator persistence and JMS datastores.
Note: If a license file cannot be found, the number of persistent monitors that the correlator allows is limited. See Running Apama without a license file.

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