Weblogic Interview Questions For Experienced

1. What is Weblogic?
Answer: WebLogic server is based on Java 2 Platform, Enterprise Edition (J2EE), the standard platform used to create Java-based multi-tier enterprise applications. J2EE platform technologies were developed through the efforts of BEA Systems and other vendors in collaboration with the main developer, Sun Microsystems.

2. Ho, do you troubleshoot Server Hang?
Answer: We can use java WebLogic.Admin PING to check if we get a normal response.
We need to take multiple thread dumps with kill -3 PID on Unix and CTLR Break on Windows.
Analyze the thread dump to find the root cause.

3. What is Node Manager?
Answer: Node Manager is a program that is used to control WebLogic Server instances. A single Node
Manager instance is used to control all of the server instances running on the same physical machine or different machine.
These instances can reside in different clusters, domains, and such. You must configure each machine in
your domain to communicate with Node Manager.

4. How to change from development mode to production mode in Weblogic 10.3?
To change Weblogic start-up mode from DEV to production. One way to change it is, by simply
editing setDomainEnv.cmd which resides in $root_domain/bin folder.
Look for the line that sets the PRODUCTION_MODE script variable: set PRODUCTION_MODE
Add false to the value of the PRODUCTION_MODE variable to ensure the server starts in development
Set true for starting in prod mode.
Save your changes and exit the text editor.

5. Why is there no polymorphic-type response from a create () or find () method?
Answer: The EJB Specification prohibits this behavior and the WebLogic.bc compiler checks for this behavior and prohibits any polymorphic type of response from a create() or find() method.
The reason they create() and find() methods are not polymorphic is similar to the reason constructors are not polymorphic in Java. The derived classes generally do not know or cannot initialize the base class properly.

6. Why did my JDBC code throw a rollback SQL Exception?
JDBC code may throw the following exception:
The coordinator has rolled back the transaction. No further JDBC access is allowed within this transaction.
The WebLogic JTS JDBC driver throws this exception when the current JDBC connection transaction rolls back prior to or during the JDBC call. This exception indicates that the transaction in which the JDBC connection was participating was rolled back at some point prior to or during the JDBC call.
The rollback may have happened in an earlier EJB invoke that was part of the transaction, or the rollback may have occurred because the transaction timed out. In either case, the transaction will be rolled back, the connection returned to the pool and the database resources released. To proceed, the JTS JDBC connection must be closed and reopened in a new transaction.

7. Inclined to build a profession as Oracle WebLogic Developer?
Then here is the blog post on Oracle WebLogic Training.
When deploying a resource adapter (.rar) to WebLogic Server, are its

8. classes placed in the WebLogic classpath?
Answer: For instance, I am deploying an EJB and a resource adapter (.rar), the EJB has no dependencies on the .rar because the EJB is writing to the common client interface (CCI). The EJB client application has sends/marshals as parameter classes that are defined in the .rar. For some reason, the EJB’s classloader hierarchy cannot find the definition of this .rar-specific class, even though the .rar is deploying successfully. I receive the following error on the EJB client:
java.rmi.UnmarshalException: error unmarshalling arguments; nested


9. How Do Stubs Function Inside Weblogic Server Cluster At The Time Of Failure?
Answer: Stubs perform the process of removing the failed instance from the list whenever there is a failure. The stub usually makes use of DNS for finding the running server and also for obtaining the list of the instances that are currently available with the application. List of the instances available with the server inside cluster gets periodically refreshment and allows in acquiring advantages associated with new servers. The advantages are gained as the server gets added to the cluster.

10. What are the applications in Websphere?

WebSphere applications use the following kinds of technologies:
Java specifications and other open standards for developing applications.
WebSphere programming model extensions to enhance application functionality.
Containers and services in the application server, used by deployed applications, and which sometimes can be extended.

11. What are Weblogic clusters?
Answer: A WebLogic Server cluster consists of multiple WebLogic Server server instances running simultaneously and working together to provide increased scalability and reliability. A cluster appears to clients to be a single WebLogic Server instance. The server instances that constitute a cluster can run on the same machine, or be located on different machines. You can increase a cluster’s capacity by adding additional server instances to the cluster on an existing machine, or you can add machines to the cluster to host the incremental server instances. Each server instance in a cluster must run the same version of WebLogic Server.
Benefits of clustering:
The capacity of an application deployed on a WebLogic Server cluster can be increased dynamically to meet demand. You can add server instances to a cluster without interruption of service, the application continues to run without impact to clients and end-users.
In a WebLogic Server cluster, application processing can continue when a server instance fails. You “cluster” application components by deploying them on multiple server instances in the cluster, so, if a server instance on which a component is running fails, another server instance on which that component is deployed can continue application processing.

12. What type of object is returned by ResultSet.getObject()?
Answer: WebLogic driver for Oracle always returns a Java object that preserves the precision of the data retrieved. WebLogic driver for Oracle returns the following from the getObject() method:
For columns of types NUMBER(n) and NUMBER(m,n): a Double is returned if the defined precision of the column can be represented by a Double; otherwise, BigDecimal is returned.
For columns of type NUMBER: Because there is no explicit precision, the Java type to return is determined based on the actual value in each row, and this may vary from row to row. An Integer is returned if the value has a zero-valued fractional component and the value can be represented by an integer.
For example, 1.0000 will be an integer. A long is returned for a value such as 123456789123.00000. If a value has a non-zero fractional component, a Double is returned if the precision of the value can be represented by a Double; otherwise, a BigDecimal is returned.

13. How do I call Oracle stored procedures that take no parameters?
Here is what we use that works:
CallableStatement cstmt = conn.prepare all(“Begin to proclaim;
where the program is the name of an Oracle stored procedure. This is standard Oracle SQL syntax that works with any Oracle DBMS. You might also use the following syntax:
CallableStatement cstmt = conn.prepare all(“{call procName};”);
This code, which conforms to the Java Extended SQL spec, will work with any DBMS, not just Oracle.

14. State some of the features present in Websphere?
Supports the Servlet/JSP container functionality which runs on top of HTTP.
Supports HTTP servers such as IBM HTTP server, MS IIS and Netscape iPlanet server.
Supports HTML pages, Setvlets, Java Server Pages and XML.
Supports EJB component model, Workload Management. WLM supports multiple servers within a single administrative domain.

15. What are the various causes for OUT OF MEMORY?
a) Insufficient heap size, not able to match the extra load.
b) Objects lying too long, like HTTP Sessions.
c) Memory leak in application code.
d) Full GC not happening due to JVM Bug.

16. How Many Way To Start And Stop Weblogic Servers?
There are many ways to start & stop WebLogic Admin and managed servers:
You can start and stop Admin Server using :
1) Script
2) “Java Weblogic.server “command(The weblogic.Server class is the main class for a WebLogic Server instance)
3) From startup option on windows
4) WLST with or without node manager
You can start managed servers using :
1) scripts
2) admin console
3) using WLST
4) using node manager
5) java WebLogic.server command( The weblogic.Server class is the main class for a WebLogic Server instance )

17. How To Know Weblogic Version?
Answer: In the WebLogic console, in the left navigation tree, click on “Environment”, then “Servers”. Then click on one of the servers in the list. Then click on the “Monitoring” tab. Look at the “WebLogic Version” field.

18. Explain Deployment Descriptors?
Answer: Deployment descriptors are associated with almost all the modules as well as applications. The deployment descriptors can be seen in the form of XML documents and they are capable of describing the contents that are part of the directory or the jar file. J2EE specifications usually define the standard as well as the deployment descriptors which are portable for J2EE applications and modules.

19. What Is The Name Of Default Jvm That Is Made Used For Weblogic?
Answer: The sun hotspot JDK default is made used for development, JRockit is the one used for the production of WebLogic 11g as well as 12c. The operating system is another factor that helps in choosing the certified JDK JVM.

20. What is Thread dump?
Thread Dump is a textual dump of all active threads and monitors of Java apps running in a
Virtual Machine.

21. What is the Managed Server?
Answer: A managed server is a server in a domain that is not the Administration server. It contacts the
administration server for configuration information. It runs a business application in a production
environment. It is independent of all other Managed servers in a domain (unless they are not in a cluster).
You can have many managed servers in a domain. Individual managed servers are typically added for capacity and application isolation.

22. Explain the attribute CHANNEL in WebSphere MQ?
Answer: A channel is a connection that is to establish a link between a sending channel and receiving channel. A channel has a sender channel at the local queue manager and receiver channel at the remote queue manager. These two channels consist of the same name and together make one channel.
The CHANNEL attribute is used with WebSphere MQ applications, to specify the channels for receiving and sending messages in a file that defines sender and receiver channels.

23. How to start Node Manager?
To Stop Node Manager
In Unix/Linux, kill the process –
kill -9 ps -ef | grep -i nodemanager.javahome | grep -v grep | awk {‘print $2’} | head -1
How to start/stop Node manager

24. What is the difference between Multicast and Unicast?
Answer: Unicast is the method used in the clustering technique where there is cluster master and each server should ping to this cluster master for informing that the server is alive.
Multicast: It is a kind of clustering system where there is no cluster master and each and every server needs to ping each other for informing their existence. Multicasting has many messages to be sent in the form of ping as each server needs to inform all others about its existence. This condition creates much complexity associated with the method compared to unicast.

25. What is the difference between WebLogic and WebSphere?
Answer: Though the functionality of these two products is closer, there are minor differences in the standards that support. These differences are:
WebSphere’s focus is more on connectivity, integration and web services whereas WebLogic’s focus is more on emerging standards and ease-of-use of J2EE.
WebSphere’s performance is better in terms of implementations of J2EE is little more involved, and supports more integration and transaction management
WebLogic is supported by default transaction attribute – “Supports”, whereas WebSphere has not default transaction attribute.
WebSphere strictly follows J2EE architecture.

26. How to troubleshoot and overcome such issues?
Gather memory data by enabling GC verbose.
If its due to Http Session, timing out https session after certain interval might help.
Look into the code for JDBC connection handling.
Optimizing the heap size according to the load.

27. How to troubleshoot it?
In a Solaris environment, we need to take pstack and prestack and see what the threads are doing.
In Windows, we need to use pslist and process explorer.

28. What is Clustering and what is achieved through it?
Clustering is the grouping together of servers for the purpose of high availability and scalability.
Load balancing and Failover is achieved.

29. What is the difference between Development mode and Production mode of Weblogic Server?
Development Mode:
1. The default JDK for development domain is Sun Hotspot.
2. You can use the demo certificates for SSL.
3. Auto deployment(to admin server only) is enabled.
4. Server instances rotate their log files on start-up.
5. Admin Server uses an automatically created boot.properties during start-up.
6. The default maximum capacity for JDBC Datasource is 15.
7. The debug flag which is used to start the WebLogic Workshop Debugger is enabled.
8. In Development Mode any configuration change is done by a user doesn’t need him to take a Lock and Edit session.
9. Availability of web service test client.
10. Node manager username and password: Default Admin credentials.
11. Availability of Classloader Analysis Tool: Yes.
12. The default start parameters when using Sun JDK and the default start
Production Mode:
1. The default JDK for production domain is JRockit.
2. If you use the demo certificates for SSL a warning is displayed.
3. Auto deployment(to admin server only) is disabled.
4. Server instances rotate their log files when it reaches 5MB.
5. Admin Server prompts for username and password during start-up.
6. The default maximum capacity for JDBC Datasource is 25.
7. The debug flag which is used to start the WebLogic Workshop Debugger is disabled.
8. In Production Mode the user needs to procure a Lock and Edit session before trying to make any configurational changes.
9. No Availability of web service test client.
10. Node manager username and password: Randomly generated
11. Availability of Classloader Analysis Tool: No.

30. What are deployment descriptors?
Answer: Modules and applications have deployment descriptors—XML documents—that describe the contents of the directory or JAR file. Deployment descriptors are text documents formatted with XML tags. The J2EE specifications define a standard, portable deployment descriptors for J2EE modules and applications.

31. What is the default JVM used for Weblogic?
Answer: Sun Hotspot JDK default for Development installation, JRockit is for Production mode for WebLogic 11g and 12c. Operating environment also factor to select the Certified JDK JVM. If you want to change you need to specify it.

32. What is a domain template?
Answer: A domain template is a jar file default one is wls.jar file, which is ‘/bea/weblogic81/common/templates/domains/, it has all the features that are required for the standard WebLogic domain, we can even create domain template of our own configuration. by this template, we mustn’t configure every time we create a new domain.
By using a template, we can
Create servers
Configure services such as JMS, JDBC, Applications

33. How many ways take Thread Dumps?
Answer: we have to take a Thread dumps many times when we faced issues. We can choose one Procedure. For analyzing take dumps some Intervals.

34. How can I use ANT to run a Java application?
The following is an example to run a Java application in using ANT:
<jvmargvalue=”-dname=${name}” style=”padding: 0px; margin: 0px; color: rgb(0, 0, 0); font-family: Helvetica, “Open Sans”, Arial, sans-serif, Verdana; font-size: 15px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: 2; text-align: left; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px;”>

35. Explain how to debug my ANT script ?
Answer: The echo can be used as the alert () of the JavaScript.
Use project.log(“msg”) in javascript or custom ant task.
Run ANT with -verbose, or even -debug, to get more information on what it is doing, and where.

36. What is J2ME?
– J2ME stands for Java 2 Platform Micro Edition.
– It is targeted at small, standalone or connectible consumer and embedded devices.
– This technology consists of both a programming language and a software platform.
– It is a highly optimized version of JRE and consists of JVM and a set of APIs, which is suitable for simple runtime environments.
– It provides a robust and flexible environment for running applications.

37. What is the CDC?
– CDC stands for Connected Device Configuration.
– It is a set of tools for developing applications that run on a range of network-connected consumer and embedded devices that support the Java ME CDC application framework.
– It is a JVM that is highly optimized for resource-constrained devices.
– It is used for bigger devices, such as set-top box and PDAs.
– CDC has more memory and more robust network connectivity.

38. What is CDMA?
– CDMA (Code Division Multiple Access) is a multiplexing technique based on spread spectrum approach.
– This allows several users to share a bandwidth of frequencies.
– In this, a special coding scheme is used where each transmitter is assigned a code to allow multiple users to be multiplexed over the same physical channel.
– It refers to any several protocols which are used in second and third-generation wireless communication.
– It employs analog to digital conversion in combination with spread spectrum technology.

39. What is Telematics?
– Telematics is a GPS technology that provides location-based service to track latitude and longitude of a vehicle.
– It outputs maps in LED consoles mounted on dashboards.
– The server is connected to remote processing centers which provide data, voice and Internet services.
– Telematics is the technology of sending, receiving and storing information relating to remote objects, such as vehicles, telecommunication devices.

40. How to configure JMS?
JMS (Java Message Service) is a standard API for accessing enterprise messaging systems. Specifically, WebLogic JMS:
Enables Java applications sharing a messaging system to exchange messages.
Simplifies application development by providing a standard interface for creating, sending, and receiving messages.
Using the Administration Console, you define configuration attributes to:
1. Create JMS servers and target a WebLogic Server instance or a Migratable Target where the JMS server will be deployed.
2. Create and/or customize values for JMS servers, connection factories, destinations (queues and topics), JMS templates, destination sort order (using destination keys), persistent stores (file or JDBC), paging stores, session pools, and connected consumers.
3. Define message and/or bytes thresholds and quotas, as well as a maximum allowable message size on your JMS servers, destinations, and templates.
Enable any desired WebLogic JMS features, such as:
Server clustering using multiple connection factories.
High availability and load balancing for destinations across a cluster by using distributed destinations.
Persistent messages and durable subscribers
Paging out message bodies during peak load periods to free up memory.
Controlling message flow during peak load periods, including blocking message producers.
Establishing a message expiration policy to ensure that expired messages are cleaned up immediately.
Preventing message quota errors by temporarily blocking message producers from sending messages to a destination when it exceeds its specified maximum message quota.
Concurrent message processing via session pools.

41. What you Can Do with Node Manager?
We can manage the whole gamut of activities from the Node manager
1) Start, Shut Down, and Restart an Administration Server
2) Start, Shut Down, Suspend, and Restart Managed Servers
3) Monitor Servers and View Log Data

42. What is extended deployment in WebSphere?
WebSphere Extended Deployment delivers enhanced Qualities of Service with features for optimizing IT resources.
The suite comprises of 3 products:
WebSphere Virtual Enterprise:
It increases flexibility and agility to ensure business process integrity, improve service, application performance, and better manage health.
It provides application infrastructure virtualization capabilities that lower costs required to create, manage, and run enterprise applications and an SOA environment.
WebSphere extreme Scale:
It is an essential IBM software technology for conducting extreme transaction processing.
It allows business applications to process exceptionally large volumes of transactions with extreme efficiency and linear scalability.
It provides transactional integrity and transparent failover to ensure high availability, high reliability, and constant response times.
It operates as an in-memory data grid that dynamically caches, partitions, replicates, and manages application data and business logic across multiple servers.
Compute Grid:
Enables the scheduling, execution, and monitoring of batch type jobs with enhanced service policy and workload management

43. What are the Admin Default ports?
Answer: The non-SSL listen port for the Administration Server’s default network configuration is 7001 by default.
The SSL listen port for the Administration Server’s default network configuration is 7002 by default.
WebLogic Admin servers and Managed servers could communicate with Admin port which is separate network channel. So that other communications can be run on different networks.

44. How can default JVM be changed to others?
Answer: For changing the JVM can be done by following the steps below.
1)You should first set the JAVA_HOME in the start script of the server.
2)Change the config.xml of the domain for using the JRockit javac.exe
3) Remove any kind of switches specific to Sun JVM from start scripts of the server.

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