Correlating Output Adapter ActiveActiveGroupBean

20-12 Oracle Complex Event Processing Developers Guide When an Oracle CEP server rejoins the multi-server domain, if your application is an Oracle CEP high availability Type 1 application the application must generate exactly the same sequence of output events as existing secondaries, it must wait the warm-up-window-length time you configure for the Oracle CEP high availability output adapter before it is available as a secondary. To implement this high availability quality of service, you configure your EPN with a high availability input adapter after each input adapter and a high availability correlating output adapter before each output adapter. To increase scalability, you can also use the cluster groups bean with high availability quality of service. For more information, see: ■ Section 21.1.4, How to Configure Precise Recovery With JMS ■ Section 23.2, Configuring Scalability With the ActiveActiveGroupBean

20.3 Designing an Oracle CEP Application for High Availability

Although you can implement Oracle CEP high availability declaratively, to fully benefit from the high availability quality of service you choose, you must design your Oracle CEP application to take advantage of the high availability options that Oracle CEP provides. When designing your Oracle CEP application for high availability, consider the following : ■ Section 20.3.1, Primary Oracle CEP High Availability Use Case ■ Section 20.3.2, High Availability Design Patterns ■ Section 20.3.3, Oracle CQL Query Restrictions

20.3.1 Primary Oracle CEP High Availability Use Case

You can adapt Oracle CEP high availability options to various Oracle CEP application designs but in general, Oracle CEP high availability is designed for the following use case: ■ An application receives input events from one or more external systems. ■ The external systems are publish-subscribe style systems that allow multiple instances of the application to connect simultaneously and receive the same stream of messages. ■ The application does not update any external systems in a way that would cause conflicts should multiple copies of the application run concurrently. ■ The application sends output events to an external downstream system. Multiple instances of the application can connect to the downstream system simultaneously, although only one instance of the application is allowed to send messages at any one time. Within these constraints, the following different cases are of interest: ■ The application is allowed to skip sending some output events to the downstream system when there is a failure. Duplicates are also allowed. For this case, the following Oracle CEP high availability quality of service options are applicable: