35+ WebLogic Interview Questions & Answers [ ORACLE TRICKS ]
WebLogic Interview Questions and Answers

35+ WebLogic Interview Questions & Answers [ ORACLE TRICKS ]

Last updated on 04th Jul 2020, Blog, Interview Questions

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Prabhu (Sr Administrator - Weblogic )

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These WebLogic Interview Questions have been designed specially to get you acquainted with the nature of questions you may encounter during your interview for the subject of WebLogic . As per my experience good interviewers hardly plan to ask any particular question during your interview, normally questions start with some basic concept of the subject and later they continue based on further discussion and what you answer.we are going to cover top 100 WebLogic  Interview questions along with their detailed answers. We will be covering WebLogic  scenario based interview questions, WebLogic  interview questions for freshers as well as WebLogic  interview questions and answers for experienced. 

1. Explain deployment descriptors?


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.

2. What is web.xml ?


Web.xml is an XML document that is mainly for application purpose and it helps in listing out the J2EE components and configuration that of your application in J2EE modules format.

3. What is the name of default JVM that is made used for WebLogic?


The sun hotspot JDK default is made used for development, JRockit is the one used for production of WebLogic 11g as well as 12c. Operating system is another factor that helps in choosing the certified JDK JVM.

4. Explain the methods for providing user credentials for starting the server?


At the time of the creation of domain, the wizard for setting configuration asks for the details like user name, password etc. from the user who is logging in for the first time as an administrator. If the domain is created in development mode, the configuration wizard saves the encrypted password as well as the username inside an identity file. This file is available for reference during the time of booting so that in the absence of this file, system can prompt the user for the purpose of entering credentials. A new boot – identity file can be created if you want to change the use credentials or else if you are having the requirement of creating domain in the production mode.

5. Is there any possibility for starting managed server during the absence of administrator server?


The usual process is that in case of any difficulty for the manager server to get connected to any administration server at the time of start up, there is an option for the managed server to retrieve the configuration related to it from the configuration files as well as other files involved.  The information thus retrieved cannot be altered and it is possible only when the administration server is really available. When the administration server is unavailable, then the managed server enters into its independence mode for carrying out its operations.

6. Explain WebLogic server.


This is a kind of server that supports various services as well as infrastructure that are related with JEE applications. WebLogic server is capable of deploying components as well as applications through WSDL, UDDI and SOAP. This server gets configured as a web server by making use of HTTP listener for supporting the HTTP. Web servers like that of Apache, Netscape and Microsoft are utilized.  The configuration of a web server allows WebLogic is capable of providing services to dynamic and static requests that are usually generated by servlets, HTML and JSP.

7. What are the capabilities of WebLogic server?


There are various capabilities associated with WebLogic server and they are

  • Changes in dynamic configuration.
  • Production application redeployment
  • Rolling upgrades.

8. Explain about the function associated with T3 in WebLogic server ?


T3 provides enhancements support for the messages of WebLogic server. The enhancements comprise of the object replacement, the working of the seblogic server – clusters and also HTTP. T3 also performs serialization of java object and also predation of RMI. T3 can be considered as a superset associated with java object. T3 is mandated between WebLogic servers, programmatic clients and cluster associated with WebLogic server. The protocols HTTP and IIOP are made used for enabling communication between WebLogic server and processes.

9. Explain the use of HTTP ?


HTTP is the protocol that is made used for the purpose of enabling communication between the WebLogic server and processes.

10. Explain the functionality of IIOP ?


IIOP is a kind of protocol helpful in enabling the communication between WebLogic server and object request broker.

11. How do you set a CLASSPATH in a WebLogic server?


You can use the script files from WebLogic to set CLASSPATH for the requirements. These are the files that we have to use based on the OS type (Windows or Linux):

  • WL_HOME/server/bin/setWLSEnv.cmd for Windows
  • WL_HOME/server/bin/setWLSEnv.sh for Linux

12. What are the different ways used to deploy your applications in a WebLogic server?


Following are the ways to deploy your applications into a WebLogic server:

  • Via Console
  • Via Auto-deployment
  • Via CLI (Command Line Interface) – weblogic.deployer
  • Via ANT / WLST

13. How do you turn off the auto-deployment feature in WebLogic server?


Auto deployment mode feature of WebLogic server works for the development mode, where it checks every 3 seconds to see if there are any new applications available or any new changes available for the existing applications and deploys them. To disable the automatic deployment, these are the available options:

  • Selecting Production mode checkbox from the Administration Console for the necessary domain.
  • On CLI, use option -Dweblogic.ProductionModeEnabled=true when starting the respective domain’s Administration Server.

14. What is your understanding on BSU in WebLogic server?


WebLogic Smart Update or BEA Smart Update utility (BSU) is a utility available to update or apply patches on WebLogic Servers. It can be found under the following folder (WL_HOME/utils/bsu).

15. What is an Administration server?


Administration Server can be understood as the one-stop solution for all configuration in a given domain. We can also monitor all the resources of a domain from the Administration server as well.

16. How do we access the Admin console?


You can access the WebLogic server’s admin console by entering the administration machine name and port in the navigation bar of a browser. There you’ll be prompted to provide the login credentials.

17. What is the default port of WebLogic admin server?


The default port of the WebLogic Admin server is 7001 and for SSL it is going to be 7002.

18. What are Managed servers?


Managed servers within a WebLogic server is that component which hosts the business applications, application components, webservices and the other resources that are associated with these artefacts. In order to maintain the performance statistics, the domain’s configuration document is maintained as a read-only copy. This is synchronized when the Managed server starts up connecting to the domain’s Administration Server.

19. What are the different ways to configure a Managed server in WebLogic server?


The Managed servers can be configured in a WebLogic server in three different ways, which are as follows:

20. How do we start a Managed server when there isn’t an Administration server?


When the WebLogic server’s Administration server is not available, then the Managed server goes into an independent mode to carry out its own set of operations. But in usual, the Managed server connects with the Administration server during its own startup and always maintains a read-only copy of the configuration file with itself.

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    21.What is weblogic server?


    Oracle WebLogic Server is J2EE Server (earlier known as BEA WebLogic Server) similar to  Oracle Application Server.

    22.What oracle weblogic server includes?


    Oracle weblogic server includes

    • Domain
    • cluster
    • servers

    23.We often see BSU when using weblogic. What is the meaning of BSU ?


    Oracle bought Weblogic from BEA. BSU Stands for Bea Smart Update.This utility is used to apply the WebLogic Server Patches. In simple terms, it is first letter of name of founders  Bill Coleman, Ed Scott and Alfred Chuang.

    24.What is domain in WebLogic ?


    Domain is a group of WebLogic server resources like admin server, managed server, jms,connection pool, data sources etc or whatever the resource you know of WebLogic server.  since domain is the basic unit you have to create after installation and everything created and configured under a domain.There can only be one administration Server in domain and zero to N Managed Server.

    25.What is Administration Server ?


    Admin server is the central point from where you can configure, Monitor and manage all  resources of a domain.

    Administration Server is WebLogic Server instance that maintains configuration data for a  domain. You can deploy your application on administration Server but it is recommended to  create managed Server and deploy your application in managed server and leave  Administration domain for configuration and maintenance.

    26.What is Managed Server ?


    It is an instance of your WebLogic server that is running on JVM and has its own  configuration.

    In Managed server we will deploy the java components

    • Web Applications
    • EJB Applications
    • JMS Applications
    • Web services

    27.Can we start a Managed Server if the Administration Server is unavailable?


    By default, if a Managed Server is unable to connect to the specified Administration Server during startup, it can retrieve its configuration by reading a configuration file and other files directly. You cannot change the server’s configuration until the Administration Server is available. A Managed Server that starts in this way is running in Managed Server Independence mode

    28.What is the easiest way to set the classpath?


    WebLogic Server installs the following script that you can use to set the classpath that a server requires

    WL_HOME\server\bin\setWLSEnv.cmd (on Windows)

    WL_HOME/server/bin/setWLSEnv.sh (on UNIX)

    where WL_HOME is the directory in which you installed WebLogic Server

    29.What is Cluster in WebLogic ?


    Two or more managed server becomes or forms the cluster in a domain and cluster handle the  load balancing across the cluster.

    Group of WebLogic Managed Server Instances that work together to provide high availability  and scalability for applications is called cluster. WebLogic Servers with in cluster can  run on same machine or different machines. These are also called as managed Server   cluster.

    30.What is Server


    Server is an instance of your WebLogic which is running on a JVM and has dedicated RAM.

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    31.What are deployment descriptors?


    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 standard, portable deployment descriptors for J2EE modules and applications.

    32.What is the default JVM used for Weblogic?


    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.

    33.How to configure a DB connection pool?


    Choose the DB type (Oracle, Sybase, Mysql, etc…).

    • Then choose the driver type for the DB.
    • Give the connection pool name.
    • Give the DB Service ID, schema name and password.
    • Then it will ask for testing the connection pool/DataSource.
    • After successful connection, it will ask you to create and deploy the connection pool target to server or cluster. After creating new connection pool always point the jdbcstore to the connection pool created. This is required because A JMS JDBC store will be used for persistent messaging.
    • After each JDBC connection, we must restart the server if there is startup classes dependancy exists otherwise no restart required in WebLogic 9.x and higher versions.

    34.What are the modes of operation for Weblogic server domains?


    There are two modes: Development and production mode:

    Development mode:

    You use development mode while you are developing your applications. Development mode uses a relaxed security configuration and enables you to auto-deploy applications.

    You can use the demonstration digital certificates provided by the WebLogic Server security services. With these certificates, you can design your application to work within environments secured by SSL.

    WebLogic Server instances can automatically deploy and update applications that reside in the domain_name/applications directory.

    When you start a server, the server automatically renames (rotates) its local server log file as server-name.log.n. For the remainder of the server session, the server rotates its local log file whenever the size of the file reaches 500 kilobytes.

    The default number of threads available to Execute Queues is 15.

    The default capacity is 15 JDBC connections.

    35.What is a domain template?


    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 is required for the standard weblogic domain, we can even create domain template of our own configuration. by this template we don’t must configure every time we create a new domain.

    By using template, we can

    • Create servers
    • Clusters
    • Machines
    • Configure services such as JMS, JDBC, Applications

    36.What is the function of T3 in WebLogic Server?


    The enhancements support for WebLogic Server messages is provided by T3. These enhancements include object replacement, which work in WebLogic Server clusters’ context and HTTP. Java Object Serialization, RMI predation is done by T3. T3 is superset of java Object. Serialization and RMI can be done over T3.

    Between WebLogic Servers, and between programmatic clients & a WebLogic Server cluster, T3 is mandated. To communicate between processes and WebLogic Server, the protocols HTTP and IIOP can be used and optional. The HTTP is used to communicate between a browser and WebLogic Server. The IIOP is used to communicate between an Object Request Broker and WebLogic Server

    37.How do stubs work in a WebLogic Server cluster?


    The enhancements support for WebLogic Server messages is provided by T3. These enhancements include object replacement, which work in WebLogic Server clusters’ context and HTTP. Java Object Serialization, RMI predation is done by T3. T3 is superset of java Object. Serialization and RMI can be done over T3.

    Between WebLogic Servers, and between programmatic clients & a WebLogic Server cluster, T3 is mandated. To communicate between processes and WebLogic Server, the protocols HTTP and IIOP can be used and optional. The HTTP is used to communicate between a browser and WebLogic Server. The IIOP is used to communicate between an Object Request Broker and WebLogic Server.

    38.What happens when a failure occurs and the stub cannot connect to a WebLogic Server instance?


    The stub removes the instance that is failed from its list, when a failure occurs. The stub uses DNS again for finding a running server and obtains a current list of instances, when there are no servers left in its list. The list of available server instances in the cluster will get periodical refreshment, which allows making the advantage of new servers. This is because; the servers are added to the cluster.

    39.What is the difference between weblogic and websphere?


    Though the functionality of these two products are 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.

    40.How do you differentiate between a server hang and server crash issue?


    When a Server crahes, the JAVA process no longer exists. When the Server is hung, it stops responding.

    We can use the weblogic.ADMIN utilty to ping the server. In case of a hang situation we can take multiple thread dumps and analyze the cause of hang.

    41.What can be the various reasons for a server crash?


    • Native IO
    • SSL Native Libraries
    • JVM
    • Supported Configuration
    • JDBC Driver issue

    42.How do you troubleshoot a crash?


    • JVM crash generates a hs_err_pid file. We need to look into the stack trace of the hs_err_pid file .
    • If the thread is from a native io, we need to disable native io.
    • if the stack trace is from the driver, we need to get in touch with the drive team.
    • Quite possibly its a problem with driver. Changing the type of driver can be a workaround.
    • If the thread shows it coming from an optimized code, we can turn of optimization.
    • If the stack is from native calls of application, its a bug with the application and it has to b modified.

    43.Ho do you troubleshoot Server Hang?


    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.

    44.What can be the reasons of Server hang?


    Memory leak, databse query taking a long time to return, Deadlock.

    45.What is memory leak?


    Memory leak is when objects are not romved from the heap even when they are not required.

    46.What are the various causes for OUT OF MEMORY?


    • Insufficient heap size, not able to match the extra load.
    • Objects licing too long, like HTTP Sessions.
    • Memory leak in application code.
    • Full GC not happening due to JVM Bug.

    47.How to troubleshoot and overcome such issues?


    • Gather memory data by enabling GC verbose.
    • If its due to Http Session, timing out http session after certain interval might help.
    • Look into the code for jdbc connection handling.
    • Optimizing the heap size according to the load.

    48.When does High CPU Usage occur?


    It occurs when one process or one thread utilizes unexpectedly high proportion of CPU.

    49.How to troubleshoot it?


    In Solaris environment, we need to take pstack and prstack and see what the threads are doing.

    In Windows we need to use pslist and process explorer.

    50. How many ways take Thread Dumps?


    we have to take a Thread dumps many times when we faced issues. We can choose one Procedure. For analyzing take dumps some Intervals.

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    51. How can I use ANT to run a Java application?


    • <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;”>

    52. Explain how to debug my ANT script ?


    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.

    53. 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.

    54. 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.

    55. 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.

    56. 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.

    57. 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:

    • Create JMS servers and target a WebLogic Server instance or a Migratable Target where the JMS server will be deployed.
    • 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.
    • Define message and/or bytes thresholds and quotas, as well as a maximum allowable message size on your JMS servers, destinations, and templates.

    58. What Is Weblogic?


    WebLogic is a J2EE application server and also an HTTP web server by Oracle , for Unix, Linux, Microsoft Windows, and other platforms. WebLogic supports Oracle, DB2, Microsoft SQL Server, and other JDBC-compliant databases.

    59. What are the Basic Components Of Weblogic Server?


    These are the basic weblogic components

    • Domains
    • Admin Server
    • Managed Server
    • Node Manager
    • Weblogic Server Cluster

    60. What Is The Server


    A server is an instance of weblogic.Server executing in a Java Virtual Machine (JVM).

    A server:

    • Runs on a designated Oracle WebLogic Server machine
    • Has a dedicated amount of RAM
    • Is multithreaded

    Two types of servers:

    •  Administration Server
    • Managed Server

    61. What Is The Managed Server?


    Managed server is a server in a domain that is not the Administration server. It contacts the administration server for configuration information. It runs 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.

    62. How Many Types You Configure Managed Server In Weblogic Server?


    Three types

    • Domain Configuration Wizard
    • Administration Console
    • Weblogic Scripting Tool

    63. What Is Node Manager?


    Node Manager is 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.

    64. How Administration Server And Managed Servers Will Interact?


    The Administration Server stores the master copy of the domain configuration, including the configuration for all Managed Servers in the domain. Each Managed Server stores a local copy of the domain configuration file. When a Managed Server starts, it connects to the Administration Server to synchronize the configuration. When the configuration is changed, the Administration Server sends the changed configuration to the Managed Servers.

    65. What Are The Supported Installation Modes For Weblogic Server


    • Graphical mode
    • console mode
    • silent mode

    66. How Do I Turn The Auto-deployment Feature Off?


    The auto-deployment feature checks the applications folder every three seconds to determine whether there are any new applications or any changes to existing applications and then dynamically deploys these changes.

    The auto-deployment feature is enabled for servers that run in development mode.

    To disable auto-deployment feature, use one of the following methods to place servers in production mode:

    =>In the Administration Console, click the name of the domain in the left pane, then select the Production Mode checkbox in the right pane.

    =>At the command line, include the following argument when starting the domain’s Administration Server:


    Production mode is set for all WebLogic Server instances in a given domain.

    67. How Managed Servers Communicate With Each Other?


    Managed servers communicate each other using t3 protocol internally.

    68. What Is A Thread Dump? How Will You Take In Unix/linux And Windows?


    A Java thread dump is a way of finding out what every thread in the JVM is doing at a particular point in time. This is especially useful if your Java application sometimes seems to hang when running under load, as an analysis of the dump will show where the threads are stuck.

    • Linux : kill -3 <ps_id>
    • Windows (console mode) : crtl+break
    • Windows (service) : beasvc -dump -svcname:mydomain_myserver

    69. What Is Core Server Tuning?


    This is the process involving the tuning of work manager, chuck size, performance packs, chunk pool size and connection backlog buffering.

    70. How Many Weblogic Servers Can Be Held Inside A Multi-processor Machine?


    There is no limitation for the number of servers

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    71. What Is A Stage Deployment?


    Stage deployment is a kind of process in which the admin gets a physical copy which is distributed to the other instances.

    72. What is a Weblogic Server and explain its architecture?


    A Weblogic Server is an application server that complies with Java EE standards developed by Oracle Corporation. It has different features and functionalities which supports the deployment and maintenance of Java Enterprise applications along with some infrastructural applications. It has client options with rich features such as Java clients with RMI, SOAP clients or any SOAP web services platform, web services with flexible options, enterprise scalability in e-businesses, security and many other messaging services. It has a different software component tiers in its architecture. It is of multi-tier architecture and contains client tier, middle tier, and back-end tier. The client tier can be of any web-based browser, mobile devices, or any other Java or GUI clients. The middle tier is the Weblogic server and Backend tier contains different applications or databases.

    73. What are the different application layers of Weblogic Server?


    The Weblogic Server has different Application layers such as the Presentation layer, Business Layer and Service Layer. The different types of Application Layers in a Weblogic Server are as below–

    • Presentation Layer: This presentation logic layer contains Server containers or any web application containers that will render web page content using technologies such as Servlet, JSP or HTML formats.
    • Business Layer: This business layer contains containers which will hold business logic along with any Session Beans or Entity Beans. This may also contain EJB called Entity Java Beans which is of Java EE Specification.
    • Service Layer: This Service Layer contains Services and its implementation which will provide the business logic functionality as the endpoints and messaging services such as JMS, JNDI, JDBC or any other protocols such as HTTP, RMI or SSL.

    74. What is Multicasting in Weblogic Cluster?


    The process of multicasting in Weblogic cluster is defined as handling the process of messaging communications among different IP Sockets. It establishes a peer to peer communication.

    75. What is Clustering in Weblogic Server?


    This is the common Weblogic Interview Questions asked in an interview. The Clustering is the process of establishing multiple server instances to make them work together to develop high efficiency and produce greater scalability for the larger complex applications where the number of users of the application is high.

    76. What are the different Networking protocols used in the Weblogic Server?

    Ans:The different networking protocols used for the communication in the Weblogic Server are mentioned below:

    1. SOAP – It is Simple Object Access Protocol which is a messaging format used in the web services that access as a protocol for the web services standard.
    2. HTTP – Hyper Text Transfer Protocol is used in the web standards for communication.
    3. HTTP – It a secure form of HTTP used in the web browsers over Secure Socket Layer.
    4. IIOP – Internet Inter-ORB protocol which is used in the CORBA clients to establish a connection with Weblogic Server.
    5. IIOPS – It is an IIOP protocol that is of secure form.
    6. RMI – It is called as Remote Method Invocation which is used to establish a connection in the case of applications in the distributed environment.
    7. T3 – It is a Weblogic protocol that is used to establish a connection between Java applications over multiple network connections.
    8. T3S – It a Weblogic protocol that is of secure form.

    77. What is a Domain in Weblogic Server?

    Ans:The Domain in a Weblogic Server is defined as a group of resources from the Weblogic Server which contains different instances or types of servers such as Administration Server where all the resources are managed by using this group in the name of the domain. All the managed servers can be placed or grouped into a domain to manage them. A domain can handle single or multiple installations of servers.

    78. What is a Managed Server in Weblogic Server?


    A Managed Server in a Weblogic Server is defined as an instance of a Weblogic server which is used to manage the web applications deployed by the developer. These applications can be of any type such as Web Applications, Web Services, EJB Applications or JMS Applications. Every managed server will have its configuration. All the Java components can be deployed into this managed server.

    79. What are the different modes of installation of Weblogic server?


    The different modes of installation of Weblogic Server are Silent, Graphical and Console mode. Silent mode is based on the configuration files instead of manual intervention during the installation process. Graphical is a kind of GUI interaction with the user during the installation process whereas Console mode is an interactive mode similar to that of commands based.

    80. What is JVM tuning in Weblogic server?


    This is the most popular Weblogic Interview Questions asked in an interview. The JVM tuning is the process of enhancing the performance of the JVM execution engine in the Weblogic server by configuring or changing few parameters in the server such as heap size, garbage collection etc.

    81. What is Node Manager in Weblogic server?


    Node Manager is a separate process that runs independent of the Weblogic server and is used for the operation of tasks specified for managed tasks apart from administrative management tasks.

    82. How does a server know that another server is UNAVAILABLE in a cluster?


    There are two ways by which WebLogic server makes a note of the participating server nodes’ availability:

    • If a participating server node fails to emit 3 consecutive heartbeat messages, then the other server nodes consider that this server node is OFFLINE or UNAVAILABLE.
    • If there are any kind of socket failures corresponding to a specific server node, then WebLogic considers that the server node where these socket failures are reported to be UNAVAILABLE.

    83. What are the advantages of Clustering?


    The three main advantages that WebLogic server clustering brings are as follows:

    High Availability:

    High Availability is achieved in WebLogic server by a combination of the following features – Failover, Replication and also with the migrateable services. With these, we can use WebLogic seamlessly without worrying even when a participating node is down or unavailable.

    Load Balancing:

    All server nodes are distributed to receive requests, thereby load balancing is achieved in the WebLogic server.


    We can add server instances without deteriorating or bringing down the applications – hence we can scale as per the request load. This doesn’t impact the clients.

    84. Why is the Node Manager required?


    Node Manager is a Java-based utility that comes in handy to perform some common operations for a given Managed server. It runs as a totally different service than from the WebLogic server.

    85. How does stubs work in a WebLogic Server cluster?


    Stubs perform the removal of nodes from the WebLogic server cluster, whenever it identifies one. DNS comes into picture for the stubs to identify working server nodes and the list of available nodes gets updated periodically to keep the whole cluster available.

    86. What are Unicast and Multicast in a WebLogic server?


    Unicast is an option by which a packet can be sent point to point, to a specific member but not to everyone. This makes it much more like a private conversation between two specific members instead of a group chat or etc.

    Multicast, on the other hand, is more like a broadcast UDP option by which every member in the group is notified with the packet or announcement. The defined range for Multicast addresses are to, so the message that is announced is more like a common one and available for every member.

    87. How can you differentiate between a Server hang issue and a Server crash issue?


    A server crash can be understood as the situation where the JAVA process no longer exists. On the other hand, A server hang issue is when the server doesn’t respond back with proper responses. In such a case, we can collect multiple sets of dumps from the server and analyze the issue which is causing this lowered performance.

    88. What are the possible reasons for a server crash?


    Following could be the possible reasons for a server crash, though it is not limited to just these scenarios but the reasons can span much more than these:

    • Mismatch in the JDBC driver used
    • Unsupported configuration
    • SSL native libraries
    • JVM
    • Native IO related issues

    89. How do you analyze a server crash?


    A server crash always comes with a corresponding hs_err_pid file which contains the actual cause of the crash in the first place. You can refer to this file and identify the cause of the issue and basis on that, we can take the next steps:

    • If it is a driver related issue, reach out to the respective driver teams
    • If it is related to the Native IO issue, kindly disable and find an appropriate cause.

    90. How do you go about analyzing a server hang issue?


    A server hang issue is relatively different from a server crash, where there could be possibly different sets of reasons for it to happen – lack of resources, unimaginable load, other parameters that affect the system etc.

    Firstly we can use the following command to see if you get a good response:

    • java weblogic.admin ping
    • Based on the outcome of this command, you can probably check for the cause of the issue.

    91. What are the possible causes of OUT OF MEMORY?


    There can possibly the following possibilities for an OUT OF MEMORY issue:

    • Heap size would’ve less compared to the load received
    • Resource leaks from the application code itself.
    • Any JVM bugs that alter the occurrence of a full GC
    • Placing of objects taking longer than that of a given HTTP session

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