Deployment Group and Notification Group

Understanding High Availability 20-9 ■ Section 27.2.5, Oracle Coherence Performance Tuning Options ■ Configuring the Oracle Coherence Cluster in the Oracle Complex Event Processing Administrators Guide ■ Oracle Coherence Developers Guide at http:download.oracle.comdocscdE15357_ 01coh.360e15723toc.htm

20.2 Choosing a Quality of Service

Using Oracle CEP high availability, you may choose any of the quality of service options that Table 20–1 lists. Choose the quality of service option that suits your application’s tolerance for missed and duplicate events as well as expected event throughput. Note that primary and secondary server hardware requirements increase as the quality of service becomes more precise.

20.2.1 Simple Failover

This high availability quality of service is characterized by the lowest performance overhead fastest recovery time and the least data integrity both missed events and duplicate events are possible during failover. The primary server outputs events and secondary servers simply discard their output events; they do not buffer output events. If the current active primary fails, a new active primary is chosen and begins sending output events once it is notified. During failover, many events may be missed or duplicated by the new primary depending on whether it is running ahead of or behind the old primary, respectively. During the failover window, events may be missed. For example, if you are processing 100 events per second and failover takes 10 s then you miss 1000 events The new primary enters the PRIMARY state immediately. There is no configurable readiness threshold that must be met before the new primary transitions out of the BECOMING_PRIMARY state. When an Oracle CEP server rejoins the multi-server domain, it is immediately available as a secondary. To implement this high availability quality of service, you configure your EPN with a high availability buffering output adapter with a sliding window of size zero before each output adapter. To reduce performance overhead, rather than use a high availability input adapter, use application time with some incoming event property. For more information, see Section 21.1.1, How to Configure Simple Failover . Table 20–1 Oracle CEP High Availability Quality of Service High Availability Option Missed Events? Duplicate Events? Performance Overhead Section 20.2.1, Simple Failover Yes many Yes few Negligible Section 20.2.2, Simple Failover with Buffering Yes few 1 1 If you configure a big enough buffer then there will be no missed events. Yes many Low Section 20.2.3, Light-Weight Queue Trimming No Yes few Low-Medium 2 2 The performance overhead is tunable. You can adjust the frequency of trimming to reduce the overhead, but incur a higher number of duplicates at failover. Section 20.2.4, Precise Recovery with JMS No No High