Oracle SOA BPEL Interview Questions | Part-2

11) How to increase the transaction timeouts in SOA?

For the transaction timeout needs to be increased, all the below settings timeout value needs to be changed to the expected Timeout value. 

JTA 
Engine Bean 
Delivery Bean 

12) What is Decision service?

Oracle SOA Suite provides support for Decision components that support Oracle Business Rules. A Decision component is a mechanism for publishing rules and rule sets as a reusable service that can be invoked from multiple business processes. These rules can be changed without redeploying the code.

13) Is it possible to use MS SQL Server as dehydration store with SOA Suite ?if yes how?

Yes it is possible.

To automatically maintain long-running asynchronous processes and their current state information in a database while they wait for asynchronous callbacks, you use a database as a dehydration store. Storing the process in a database preserves the process and prevents any loss of state or reliability if a system shuts down or a network problem occurs. This feature increases both BPEL process reliability and scalability. You can also use it to support clustering and failover. 

14) What is SOA governance? What are its functions?

Service-Oriented Architecture (SOA) governance is a concept used for activities related to exercising control over services in an SOA Some key activities that are often mentioned as being part of SOA governance are:

Managing the portfolio of services: This includes planning development of new services and updating current services.

Managing the service lifecycle: This is meant to ensure that updates of services do not disturb current services to the consumers. Using policies to restrict behavior: Consistency of services can be ensured by having the rules applied to all the created services. Monitoring performance of services: The consequences of service downtime or underperformance can be severe because of service composition. Therefore action can be taken instantly when a problem occurs by monitoring service performance and availability.

15) What is end point virtualization?

Generally a service bus is used for endpoint virtualization and in 11g stack; Oracle Service Bus (OSB) is the primary service bus. In exposed proxy's message flow, it can route the request to any of your environment's actual (physical) service on the basis of whatever logic.

Mediator can also be used to expose the service and in mediator routing rule, it can be routed to actual service.

16) What are DVM's and how are they helpful in SOA?

DVM-Domain Value Map is static mappings between a source and target system which can be used in transformations. The value can be changed via SOA composer.

17) What is the difference between XREF and DVM?

XREF- It is dynamic since the values to the XREF can be populated dynamically and it is stored in XREF_DATA table in SOA Dehydration store.

DVM- Domain Value Map is static mappings between a source and target system which can be used in transformations.

18) What is Dehydration store?

Dehydration store is the database where the instances get stored when it gets dehydrated by the process on the occurrence of non-idempotent activities and also stores the information on the long running processes.

19) Why we use BPEL and OSB?

OSB is the light-weight service bus wherever there is not much business logic involves and there is need to just get the message routed between the systems OSB is used where as when there is more business logic involves in the process, then BPEL will be used. 

20) How does a Async request run in the backend?

The sequences of events involved in the delivery of invoke messages is as follows:

The client posts the message to the delivery service.

The delivery service saves the invocation message to the dlv_message table. The initial state of the message is 0 (undelivered).

The delivery service schedules a dispatcher message to process the invocation message asynchronously.

The dispatcher message is delivered to the dispatcher through the afterCompletion() call. Therefore, the message is not delivered if the JTA transaction fails.

The dispatcher sends the JMS message to the queue. Places a very short JMS message in the in-memory queue (jms/collaxa/BPELWorkerQueue) in OC4J JMS. The small JMS message triggers the Worker Bean in the downstream step.

This message is then picked up by a Worker Bean MDB, which requests the dispatcher for work to execute. If the number of Worker Bean MDBs currently processing activities for the domain is sufficient, the dispatcher module may decide not to request another MDB.

MDB fetches the invocation message from the dispatcher.

MDB passes the invocation message to Oracle BPEL Server, which updates the invocation message state to 1 (delivered), creates the instance, and executes the activities in the flow until a breakpoint activity is reached.