OSB Interview Questions and Answers

Q1. What is proxy service and business service in OSB?
The objective of OSB is to route message between business services and service consumers through proxy services. Proxy services are generic intermediary web services that implement the mediation logic and are hosted locally on OSB. Proxy services route messages to business services and are exposed to service consumers.

Q2. What is Oracle Service Bus (OSB)?
Oracle Service Bus allows you to manage Web services and deliver authentic message brokering through the configuration of proxy services in the Oracle Service Bus design-time environment. Oracle Service Bus manages the routing and transformation of messages in an enterprise system to promote seamless application integration. 
Oracle Service Bus is a market-leading enterprise service bus built from the ground up for Service Oriented Architecture (SOA) life cycle management. It provides foundation capabilities for service discovery and intermediation, rapid service provisioning and deployment, and governance. This service-infrastructure software adheres to the SOA principles of building coarse-grained, loosely coupled, and standards-based services, creating a neutral container in which business functions may connect service consumers and back-end business services, regardless of underlying infrastructure.

Q3. What are the key features of Oracle Service Bus or OSB?

• Supports Multiprotocol Messaging
• Enables Location Transparency
• Handles Dynamic Routing
• Enables Message Transformation
• Enables Service Orchestration
• Supports Message Enrichment
• Provides Service Security
• Implements Service Level Agreement

Q4. What are the different types of Pipelines?
Request and Response Pipeline.

Q5. What are some of the major protocols that OSB supports?

• HTTPS
• SOAP
• JMS
• SMTP/POP/IMAP
• Tuxedo
• EJB
• Native MQ
• File
• FTP
• STFP
• Email

Q6. What is a Publish Table?
Use a publish table action to publish a message to Zero or more statically specified services.

Q7. What is a Publish Node?
Use a publish action to identify a statically specified target service for a message and to configure how the message is packaged and sent to that service

Q8. What are stages ?
Stages are OSB Message Flow component to contain the actions

Q9. What is the message flow in Proxy Services ?
Message flow in OSB is the most important part. It defines the request message flow from Start Node to Route activity and also defines the response message flow from Route to Start Node. It contains Pipeline Pairs, Branch Nodes, Route Nodes , Stages, Actions etc.

Q10. How we can connect to Database from OSB?
We need to first create one JCA based DB adapter to connect to the database. Then we need to create that JCA based Business Service. We need to call that Business Service to perform database operations.

Q11. What is SLA alert in OSB?
A service-level agreement (SLA) is a contract between a service provider and a service consumer. In OSB monitoring framework we have SLA alerts which come into picture when there is violation of service level agreements.

Q12. What is Pipeline Error Handler?
Pipeline Error Handlers are used to handle the errors occurred in Request or Response Pipleline.

Q13. Explain OSB Service Orchestration?

• Combining existing services to make new services
• This is light orchestration as compared to the BPEL orchestration in SOA which may be Synchronous/Asynchronous
• But in OSB 11g, it is stateless
• There are limitations with OSB 11g as compared to the BPEL/SOA which could be used for maintaining states for hours/days as per our business needs

Q14. What is WSDL? Explain the steps to import WSDL .
A WSDL defines the public contract (interface specification) between a client and a service, whether the service is a proxy service or a business service. It is the formal description of a Web service. A WSDL is used to describe what a Web service´s interface is, where it resides, and how to invoke it. You create the WSDL resource first since subsequent service registration tasks depend on it. The WSDL is subsequently used to register the business service with the proxy service.

Q15. How to poll file in OSB?
The proxy service should be using file transport, and also define the required components like File Mask,Polling Interval, Read Limit, Post Read Action etc.

Q16. What is Alert Destination?
Alert Destination resources capture a list of recipients that can receive alert notifications from the Oracle Service Bus. They are used by Alert actions configured in the message flow, and by SLA alert rules. An Alert destination could include one or more of the following types of destinations: Reporting Data stream, SNMP trap, E-mail, JMS queue, or JMS topic. In the case of E-mail and JMS destinations, a destination resource could include a list of E-mail addresses or JMS URIs, respectively. Alert Destinations can be re-used across alert configurations for services.

Q17. Differentiate OSB and mediator. 
Mediator is an internal component part of SCA. Mediator has the below functionality.

• Cross Referencing(XREF) : referencing key and fields from seperate systems by means of storing a mapping table.
• Domain value Maps(DVM)
• Schema Validation : Validate XML Payloads

OSB is a fully fledged standalone stateless ESB.

• The main difference is mediator is intra-composite mediation while OSB is inter-composite mediation.

Q18. What is throttling in OSB. 
Throttling is part of endpoint management where we can specify the number of parallel threads the endpoint can have.

Q19. What is split join and types of Split Join. 
Split Join is a OSB feature that is used to split input message and process them with various business logic.  There are two types

• Static Split Join : Split into fixed number of branches at the design time.
• Dynamic split join : the split is created dynamically based on the conditions defined during the design time.

Q20. What is Message Context?
All messages sent to and received by the proxy service are defined internally in the proxy service by a set of properties that holds the message data and meta-data related to that message. This set of properties is known as the Message Context (context) and is implemented using Context Variables. It is defined by an XML schema. Each Context Variable relates to a different property. Some Context Variables are predefined and others are user defined. The heart of the proxy service is the Message context. For a complete description of the Message Context and context variables used in the message flow.