Oracle SOA Interview Questions
Q1) What is SOA [Service-Oriented Architecture]?
Ans: SOA is an IT architecture strategy for business solution (and infrastructure solution) delivery based on the concept of service-orientation. It is a set of components which can be invoked, and whose interface descriptions can be published and discovered. It aims at building systems that are extensible, flexible, and fit with legacy systems. It promotes the re-use of basic components called services.
Q2) Why we need SOA?
Ans: Service is an important concept. Services can be published, discovered, and used in a technology-neutral, standard form by the set of protocols of the web services. Other than being just architecture, SOA is the policies, practices, and frameworks by which it ensures the right services are provided and consumed. It becomes critical to implement processes that ensure that there are at least two different and separate processes— one for the provider and the other for consumers, using SOA. The Business Service Bus is a starting point for developers that guide them to a coherent set that has been assembled for their domain. This is better than leaving developers to discover individual services and put them into context
Q3) Challenges faced in SOA adoption?
Ans: One of the challenges faced by SOA is managing services metadata. The second biggest challenge is the lack of testing in SOA space. Another challenge is providing appropriate levels of security. Interoperability is another important aspect of the SOA implementations. Vendor hype concerns SOA because it can create expectations that may not be fulfilled.
Q4) What is SOA governance? What are its functions?
Ans: 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 the 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.
Q5) What are the Business Benefits of Service-Oriented Architecture?
Ans: SOA can help businesses respond more quickly and economically to changing market conditions. SOA can be considered an architectural evolution. It captures many of the best practices of previous software architectures. The goal of separating users from service implementations is promoted by SOA. The goals like increased interoperability increased federation, and increased business & technology domain alignment can be achieved by SOA due to its architectural and design discipline. SOA is an architectural approach for constructing complex software-intensive systems from services. SOA realizes its business and IT benefits through utilizing an analysis and design methodology when creating services.
Q6) What are the IT Benefits of Service-Oriented Architecture?
Ans: IT benefits of SOA are:
- The ability to build composite applications is provided.
- Business services are offered across divided
- Provides truly real-time decision-making applications.
- Reliability is enhanced
- Services don't need to be at a particular system or network
- The approach is completely loosely coupled
- Hardware acquisition costs are reduced
- At every level, there’s Authentication and authorization support
- Existing development skills are leveraged
- Provides a data bridge between incompatible technologies
- The search and connectivity to other services is dynamic
Q7) Is Oracle SOA the same as Oracle Fusion Middleware?
Ans: No, because SOA is one of the parts in Fusion middleware and SOA behaves like a user interface whereas Fusion is a big platform
Q8) What is SCA?
Ans: Service Component Architecture (SCA) provides a programming model for building applications and systems based on a Service Oriented Architecture. SCA is a model that aims to encompass a wide range of technologies for service components and for the access methods which are used to connect them.
Q9) What is the SOA Suite 11g Components?
- Oracle Adapters
- Oracle Mediator
- Business Events and Events Delivery Network
- Oracle Business Rules
- Human Workflow
- Oracle Business Activity Monitoring
- Oracle Enterprise Manager
Q10) What is choreography? How does it differ from orchestration?
Ans: In choreography, there is no business process to control the integration between the systems; each system will directly integrate into the sequence whereas in Orchestration there is a business process that controls all the services (Source/Target) which is part of the integration.
Q11) What are the different design patterns in SOA?
- Asynchronous Fire and Forget
- Asynchronous Delayed Response.
Q12) In how many ways can a process be deployed?
- Using Jdeveloper
- Through Enterprise Manager Console
- Through Weblogic Scripts.
Q13) What are dspMaxThread and recieverThread properties? Why are they important?
Ans: Receiver Threads property specifies the maximum number of MDBs that process Async across all domains. Whereas the dspMaxThread is the maximum number of MDBs that process Async and threads that operate across a domain. So, we need to ensure that the dspMaxThread value is not greater than Receiver Threads.
Q14) How does an Async request run in the backend?
Ans: The sequences of events involved in the delivery of invoking messages are 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 after completion() 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.
Q15) How to increase the transaction timeouts in SOA?
Ans: For the transaction timeout needs to be increased, all the below settings timeout value needs to be changed to the expected Timeout value.
- Engine Bean
- Delivery Bean
Q16) Is it possible to use MS SQL Server as a dehydration store with SOA Suite? if yes how?
Ans: 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.
Q17) 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 the 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.
Q18) What is endpoint 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 based on whatever logic.
- A mediator can also be used to expose the service and in mediator routing rule, it can be routed to actual service.
Q19) What are DVM's and how are they helpful in SOA?
Ans: 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 the SOA composer.
Q20) 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 the XREF_DATA table in the SOA Dehydration store.
- DVM- Domain Value Map is static mappings between a source and target system which can be used in transformations.
Q21) What is a Dehydration store?
Ans: The dehydration store is the database where the instances get stored when it gets dehydrated by the process of the occurrence of non-idempotent activities and also stores the information on the long-running processes.
Q22) What is the Decision service?
Ans: 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.
Q23) Why we use BPEL and OSB?
Ans: OSB is the light-weight service bus wherever there is not much business logic involves and there is a need to just get the message routed between the systems OSB is used whereas when there is more business logic involves in the process, then BPEL will be used.
Q24) What is MDS?
- MDS –Metadata Store
- Wsdl and Schemas to be used in the process can be published to the MDS and get it used in the code by referring to the artifacts from the MDS.
- JAR (Deployment unit) size will be reduced.
- Duplication of the artifacts can be avoided between the services.
Q25) What is a XA data source? How it differs from a non-XA data source?
Ans: An XA transaction involves a coordinating transaction manager, with one or more databases (or other resources, like JMS) all involved in a single global transaction. Non-XA transactions have no transaction coordinator, and a single resource is doing all its transaction work itself (this is sometimes called local transactions).
Q26) How can we secure our web services using Oracle SOA Suite?
Ans: When accessing the services should be restricted to the group, then service should be secured via WSM (Web service Manager).
Q27) How to deploy an XSL file without the deployment of the BPEL Process?
Ans: We will directly deploy the XSLT, options: -
- Using ANT script by file replacement in the TMP folder.
- By creating a folder in the BPEL PM Installation folder and specifying its location in our BPEL code with http call and replacing our xslt to that location.
Q28) What is HA File and FTP Adapters?
In the clustered environment, File and FTP adapters should be used as HA (High-Availability)
- Inbound: It is controlled by Control Files and avoids the race between the manages servers in reading the files where the reference of the files read by the managed servers will be maintained in the control directory.
- Outbound: It is controlled by the DB Mutex table that exists in the SOA dehydration store and this avoids duplicated been written to the same file when all the managed servers in the clusters process the same messages.
Q29) What is singleton Property in SOA?
Ans: In the clustered environment when the processing of the message should happen via only one SOA managed server, then the property singleton needs to be defined at the adapter level.
Q30) What is a pick activity? Can I have a pick activity with no onMessage branch?
Ans: Pick activity picks the messages from service (Source) which has multiple operations or the BPEL process needs to receive the messages from multiple source systems. Pick activity should have at least one Message branch.
Q31) What is a flow activity? What is a flowN activity and how does it leverages the flow activity?
Ans: Flow activity is used, when parallel execution of the flow is needed and to use this property “non-blocking invoke should be set as true “at the partner link level and no. of execution of parallel flow is defined and static. Whereas in Flown the no. of execution of parallel flow is not static and it is determined during run time.
Q32) What do you mean by non-idempotent activity? Which activities are non-idempotent by default?
Ans: Activities like Pick, Wait, receive, reply, and checkpoint() are called non-Idempotent activity and during the execution of the process whenever these activities are encountered then it gets dehydrated to dehydration store.
Q33) How can we embed or use java code in BPEL?
Ans: Using JAVA embedding activity in BPEL, Java code can be embedded in BPEL and can be used.
Q34) How does pick activity differ from a receive activity?
Ans: Pick activity can act as a multiple receive activity in some business scenarios. If we have two inbound operations and both can trigger the BPEL process then we will go with pick activity as we can’t have two receive activity with the create Instance box checked.
Q35) How can we make a partner link dynamic?
Ans: If we have to send the request to a different service that has the same wsdl then a dynamic partner link will be used and using addressing schema we can set the endpoint dynamic to send the request to the desired service.
Q36) What is a nonblocking call property?
Ans: Non- blocking invoke is used when Parallel flow needs to be executed where a new thread will be created for each invokes activity and which will execute simultaneously.
Q37) What gets preference property? How do we set it and what advantage it provides?
Ans: Hard coding is not a good practice, so to avoid hard coding preference variables can be used and the value of the preference variable is accessed using get preference(). The preference variable value can be changed without redeploying the code via em console MBean property.
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Q38) How can we improve the performance of an XSL file?
Ans: By avoiding the use of various if statements and using choose and by using for-each group in place of for-each.
Q39) How do we handle transactions in BPEL?
- Property needs to be defined to start the new transaction or to continue with the same transactions.
- Property Name: Transaction and if this has value as required then the BPEL process will be continued in the same transaction whereas if the value is defined as requires new then it will start the new transaction.
Q40) What are transient and durable BPEL processes?
- Durable: It is a long-running process and initiated through a one-way invocation and do incur one or more dehydration points in the database during execution Ex: Asynchronous
- Transient: It is a short-lived process, request-response style processes, and does not incur dehydration during their process execution Ex: Synchronous.
Q41) When you will go for the Sync process?
Ans: Whenever the services return the response in few seconds, it is recommended to go for an asynchronous BPEL process if not the BPEL process should be Asynchronous the reason is calling the application can’t proceed further in case of asynchronous process.
Q42) What is a syncFileRead operation? Is an inbound or an outbound operation? Can my process begin with syncFileRead operation?
Ans: When the file has to be read in the mid of the BPEL process, then we will use syncFileRead Operation, which means some process should initiate the file read process and it is an outbound operation and process can’t begin with Sync File read.
Q43) Can we use a File Adapter to get a file without reading its content?
Ans: Yes, by selecting the Do not read file content checkbox in the Jdeveloper wizard while configuring the "Read operation."
Q44) How to increase performance increase in BPEL (Db Adapter/file adapter)?
Ans: We can increase the performance by writing indexes and sequences.
(Or) Go to application server ----> Configurations -----> Change Xml file
Q45) Explain error handling in BPEL and what is the error handling framework? How does an error handling framework better than simple error handling in BPEL?
Ans: EHF –Whenever any error is thrown by the BPEL process/Mediator then EHF will check whether existing in Fault-Bindings.xml files and if so then the action in the Fault-Policy.xml file will be taken and if the action is not found then the fault will the thrown and it will be handled in the catch block.
Q46) How do we resubmit a faulted process?
- Scenario A: The BPEL code uses a fault-policy and a fault is handled using the “ora-human-intervention” activity, then the fault is marked as Recoverable and the instance state is set to “Running”.
- Scenario B: The BPEL code uses a fault-policy and a fault is caught and re-thrown using the “ora-rethrow-fault” action, then the fault is marked as Recoverable and the instance state is set to “Faulted”; provided the fault is a recoverable one (like URL was not available).
Q47) What are Predefined errors in BPEL?
- Custom errors
- Timed out errors
- BPM errors
- Validation Errors
Q48) What is a throw activity? What it is?
Ans: Throw activity will explicitly throw the fault and this fault will get caught by the catch block and the corresponding actions will get executed.
Q49) Explain About Web service?
Ans: Web service is a type of software system which is used to exchange the data and use information from one machine to another machine through the network. Generally, Web services are based on standards such as TCP/IP, HTTP, Java, HTML, and XML. Web services are pure xml based which is used for exchange information through the Internet to direct application to application interaction. These systems include programs, objects, messages, or documents. Many software applications written in various programming languages and running on various platforms can use web services to exchange data over the computer networks. You can develop Java-based web services on Solaris and that is accessible from your V.B Program that runs on windows.
Q50) What is the difference between URI and URL?
Ans: A URI is an identifier for some resource, but a URL gives you specific information to obtain that resource. A URI is a URL and as one commenter pointed out, it is now considered incorrect to use URL when describing applications. Generally, if the URL describes both the location and name of a resource, the term to use is URI. Since this is generally the case most of us encounter every day, URI is the correct term.
Q52) What is Mediator?
- The Mediator is in charge of interconnecting, within an SOA composite application, components that expose different interfaces. Also, the Mediator can perform duties such as filtering and making routing decisions.
- The composite editor in Jdeveloper gives you the flexibility to define the interface now, to choose an existing interface, or to define the interface later as you wire components to the Mediator.
- Transforming data from one representation to another is, along with routing, one of the key functions of the Mediator.
Q53) What is the Difference between ESB and Mediator?
- In 10g for routing, a separate router needs to keep along with ESB for routing and filter expressions.
- Whereas in 11g mediator contains routing rules and filter expressions itself.
Q54) What is the difference between concrete and abstract WSDL?
- Concrete: Besides the information about how to communicate to the web service, the information on where the service exists. It has Bindings (Protocol the message should be sent) and Services(has endpoint for each binding).
- Abstract: It has information about how to communicate to the web service like types (Schema), Message (input and output messages service accepts), Operations (an operation that can be performed on this service), and port Type.