Oracle Coherence

Question

We have Oracle 10g RAC on linux supporting J2 application .
What is the relevance / value addition of "Oracle Coherence " to this app / database ?

Answer 1

Coherence is typically used in one of three ways :
1) As a cache used to offload an overloaded database server. This is primarily of value if the database server is overloaded, though in some cases caching can reduce significantly CPU usage in the application tier by avoiding client-side result set fetching and the corresponding transformation from relational to object form.
2) As a manager of application state such as HTTP sessions (via the provided Coherence*Web). Any application server could theoretically leverage Coherence to manage other state such as EJBs, but I'm not certain how many do so (as this would require code changes in the application server itself). As Rob mentioned, you could contact your provider. The symptom addressed here is usually scalability issues in the middle-tier itself.
3) As a programmatic framework, useful to solve problems that aren't readily solvable in a conventional RDBMS. This is a broader and more sophisticated problem domain, but usually it involves either needing more programmatic control than the RDBMS environment provides (e.g. a custom concurrency control strategy), or needing to bring together large numbers of CPUs and large amounts of data (e.g. large compute grids). Unlike the first two use cases, this typically requires a significant investment in code changes to the application. This is also the most common use case for Coherence.
In general, if you have no pain points in your current configuration then there is probably no reason to consider Coherence. If you have latency or throughput challenges that appear to be related to data/state, then it may be worth looking at using it in one of the above styles.
Jon Purdy
Oracle