Apama 10.3 | Apama Documentation | Developing Apama Applications | Developing Apama Applications in EPL | Using Correlator Persistence | When persistence is useful
When persistence is useful
Enabling correlator persistence is a good fit for applications in which it is unacceptable to lose any information. For example, an application for processing mortgage requests does not need to be available continuously. A small amount of downtime, especially outside business hours, might be acceptable. However, losing any state associated with a mortgage application would be unacceptable.
In such a mortgage processing application, there is unlikely to ever be a point at which there are no open applications and thus no state to preserve. But state might change over the course of weeks, rather than seconds. Enabling correlator persistence lets you implement complex event expressions such as the following:
on all LoanRequest() -> (PropertyValuation() and ProofOfIncome())
within (4 * week) ...
With persistence enabled, the event expression can still be running even if weeks elapse between when it is created and when it finally completes. Without persistence, the event expression's state is susceptible to being lost if there are system restarts, software upgrades, and the like.

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