Interview Questions for Mediator

1) What is Mediator?
Mediator is one of the components of Oracle SOA Suite tool. This component is used in below two scenarios.
1. When we need to fetch the information from source and pass to target with or without transformation.
2. When we use multiple components in one composite then it recommended that these components should interact through mediator component.

2) What is Routing rule?
 Routing rules in mediator used to define routings e.g. when we need to transfer the message from one point to another then we define one routing rule in mediator.

3) How many types of routing rules are there?
 There are two types of routing rules in mediator.
1. Dynamic routing rule
2. Static routing rule

4) What is dynamic routing rule ?
 A Dynamic Routing Rule configures a Business Rules component that uses a decision table to determine the target endpoint to which a message is routed through a dynamic external service interface. It can only be created for asynchronous interactions.

5) What is static routing rule ?.
 These rules are used when target reference is known to us. It can be created for an event subscription, an incoming operation for an synchronous and asynchronous service interaction.

6)How many types of static routing rules we have?.

 Static routing rules is of two types.
1. Sequential
2. Parallel

7)What is the difference between sequential and parallel routing rule ?.
 Below are the difference between sequential and parallel routing rules.
Sequential:
1. These routing rules evaluated and performed sequentially.
2. These routing rules executes in single thread.
3. Oracle Mediator never commits or rolls back transactions propagated by external entities.
4. Oracle Mediator always enlists itself into the global transaction propagated through the thread that is processing the incoming message.

Parallel
1. These routing rules evaluated and performed in parallel order.
2. These routing rules executes in parallel (multiples) threads.
3. Oracle Mediator commits or rolls back transactions because it is the initiator of these transactions.
4. Oracle Mediator initiates a new transaction for processing each parallel rule.

8) Can we have both sequential and parallel routing rules in one mediator?.
 yes, we can have both sequential and parallel routing rules in one mediator.

9) Which rule execute first if we have both sequential and parallel routing rules in mediator ?.
 If we have both sequential and parallel routing rules, first sequential routing rules are evaluated and actions are performed, and then parallel routings are queued for parallel execution.

10)What is re sequencing in mediator?. The resequencing feature of the Oracle Mediator reorders sets of messages that might arrive to the Oracle Mediator in the wrong sequence. You can define resequencing for all operations in an Oracle Mediator or for a specific operation.

11)Types of re sequencing in mediator ?. Below types of re sequencing available in mediator.
1. Standard (based on input Id)
2. FIFO(based on time)
3. Best Efforts

12) What is Echo in mediator ?. The purpose of the echo option is to expose all the Oracle Mediator functionality as a callable service without having to route it to any other service. For example, you can call an Oracle Mediator to perform a transformation, a validation, or an assignment, and then echo the Oracle Mediator back to your application without routing it anywhere else. For synchronous operations with a conditional filter, the echo option does not return a response to the caller when the filter condition is set to false. Instead, it returns a null response. The echo option is available for asynchronous operations only if the Oracle Mediator interface has a callback operation. In this case, the echo is run on a separate thread.

13) can we use DVM in Mediator? yes, we can use DVM’s in mediator.

14) can we validate the incoming XML message ?Yes, we can validate the incoming XML message in mediator by selecting “Validate Syntax(xsd)” checkbox.

15) What is Schematron Validation? Schematron is an XML schema language, and it can be used to validate XML contents in an XML payload.

16) Which static routing rule support fault policy ? Parallel rules only.

17) How many faults can Oracle Mediator service engine throw ?
 Only One