40 Important Weblogic Interview questions

Here is the compilation of 40 Important Weblogic Interview questions
Weblogic Interview questions

Question 1:

What is weblogic server?

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

Question 2:

What oracle weblogic server includes?

Oracle weblogic server includes


Question 3:

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.

Question 4:

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.

How to create weblogic Domain

Question 5:

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.
There will always be at least one Administration Server in a domain.

How to stop-start Weblogic server

Question 6:

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

How to stop/start Managed server

Question 7:

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

Question 8:

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

Question 9:  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.

Question 10:

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

Question 11:
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

Question 12:

Why node manager is required?

A Node Manager process is not associated with a specific WebLogic domain but with a  machine. You can use the same Node Manager process to control server instances in any WebLogic  Server domain, as long as the server instances reside on the same machine as the Node  Manager process. Node Manager must run on each computer that hosts WebLogic Server  instances. whether Administration Server or Managed Server that you want to control with  Node Manager.

Question 13:
How many types of weblogic installation ?

There are 3 types of weblogic installation.

(a) Grapical Mode (interactive GUI based)

(b) Console Mode (interactive Text Based)

(c) Silent Mode ( Non Interactive method using .xml properties file)
How to perform the weblogic Installation

Middleware Home and Weblogic Server Home directories

Question 14:
How does Cluster Communication Happen?

Members of the Cluster communicate over the Cluster Multicast IP and Port by sending  periodic heart beat messages.

Question 15:
What is the difference between the Sun JVM and BEA JRockit JVM?


The most well know JVM is the implementation from Sun. The Sun JVM is called HotSpot. The  Sun JVM is shipped in the Java Developer’s Kit (JDK) and Java Runtime Environment (JRE)  from Sun.

The BEA JRockit JVM from BEA systems is optimized for reliability and performance for  server side applications. To achieve this, BEA JRockit JVM uses technologies such as code  generation, hot spot detection, code optimization, advanced garbage collection algorithms  and tight operating system integration.

Weblogic: Sun JDK and Oracle Jrocket

Question 16: 

What are JVM Tuning Parameters.
If you have a single processor, single thread machine then you should use the serial  collector (default for some configurations, can be enabled explicitly for with -XX: +UseSerialGC). For multiprocessor machines where your workload is basically CPU bound, use  the parallel collector. This is enabled by default if you use the -server flag, or you can  enable it explicitly with -XX:+UseParallelGC. If you’d rather keep the GC pauses shorter  at the expense of using more total CPU time for GC, and you have more than one CPU, you  can use the concurrent collector (-XX:+UseConcMarkSweepGC).
Question 17:

How do you do performance tuning of WLS? What are various areas to  do it


a. Application Tuning.
jsp precompilation, ejb pool size cache..

b. OS Tuning
Setting tcp ip parameter.

c. Core Server Tuning.
tune work manager, tune chuck size and chunk pool size, using performance packs,  connection backlog buffering.

d. JVM Tuning
tuning gc strategy, monitoring garbage collection..

Question 18:

How do stubs work in a WebLogic Server cluster?

Clients that connect to a WebLogic Server cluster and look up a clustered object obtain a replica-aware stub for the object. This stub contains the list of available server instances that host implementations of the object. The stub also contains the load balancing logic for distributing the load among its host servers

Question 19:

What is HTTP tunneling? How can we configure it on WebLogic?

HTTP tuning provides a way to simulate a tasteful socket connection between WebLogic  Server and a Java client when your only option is to use the HTTP protocol. It is
generally used to tunnel through an HTTP port in a security firewall. HTTP is a stateless  protocol, but WebLogic Server provides tunneling functionality to make the connection  appear to be a regular T3Connection.
Steps to configure Http tunneling.
Login into the Admin Console, click on the server on which you want to enable he Http Tunneling feature
Click on the Protocols tab
check the “Enable Tunneling” check box.
Now you can communicate with the JVMs (Server Instances) using protocols other than t3

Question 20:

What is the difference between T3 and HTTP protocol?

WebLogic uses the T3 protocols for internal and external connections to the servers. The  T3 protocol often is used in WebLogic implementation of RMI. Proprietary of WebLogic  Server.

Http protocols are used primarily for HTTP communication between the browser and the web  server. Standard follows the W3C (World Wide Web Consortium).
Note: All of these protocols are, by default, multiplexed over the same connection to the  server’s address and port. So you can access a web page hosted by the server using a URL  such as http://host:port/page.jsp. An external client can set up an initial JNDI context  to a server using the URL t3://host:port/. All that has changed is the protocol over which  the client must communicate with the server.

Question 21:

What are the  States of the Weblogic Server?

There are 9 states of server which are given below

Shutting down

Question 22:

What is the difference between Multicast  and Unicast?


Unicast is the method used in the clustering technique where there are 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.

Question 23:

How to access admin console ?

ssl enabled admin console accessed as :
https://<hostname_or_ip_address_where_admin_server_running>:<port_on_which_admin_server_is _running>/console

Example – https://localhost:7001/console

non ssl admin console accessed as :

http://<hostname_or_ip_address_where_admin_server_running>:<port_on_which_admin_server_is_ running>/console
Example – http://localhost:7001/console

Question 24:
How many admin consoles possible in a single domain ?

only one is possible

Question 25:
What is the default port of admin server ?


Question 26:

What is config.xml in weblogic server?

config.xml is the central configuration repository for a domain. every resource you have  configured from admin console or by command line or by any other tool registered under  this file.

Question 27:

What is boot.properties file ? what is the significance of it

boot.properties is the file used by admin or managed server during startup for username  and password. it exist under your domain/servers/server_name/security folder.

When you create a domain in development mode then it creates automatically during startup  of admin server but if you create a domain in production mode then you need to define it  explicitly otherwise on every reboot of admin server it will prompt you for username and  password.
So in production mode –
Start admin server by manually passing the username and password
stop it ( press cntrl+c on the started session )
go to your domain/servers/your_admin_server/  create a folder “security”
go inside security and create a file “boot.properties” with below contents
now start the admin server, it will not prompt you for username & password further.
If you are going to start your managed servers from admin console then no need to create  this file for managed server but if you are going to start managed servers via  startManagedweblogic script then you need to follow the same above procedure for each
managed server.

Question 28:

What is actually WebLogic Cache?

Basically all the web-tier related files (.jsp .class, JSPCompiled files etc.,) get stored  in some directory. This is treated as cache whenever there is restart of a WebLogic  instance happen then the WebLogic server will look-up for last serviced object status  stored in the cache to service for any pending requests. Usually, when your EJB Classes  need sessions, JMS object requires persistance, your web-tier may contain static contents  then Cache will be used by WebLogic Application Server instance.

Question 29:
Why we need to remove Cache?

Whenever your application is accessed for the first time that fresh deployment of a new  version, WebLogic server lookup in this directory, if there are older objects persists  that will be conflict with new code objects. This is where the need of removal of cache  arises.Where there is a need of new version deployment we might need to clear the cache when the  changes to the new version is not reflected.

Generally for WebLogic 9.x and higher versions

WIN: C:\weblogic\user_projects\domains\yourdomain\servers\yourserver\tmp

UNIX: /weblogic/user_projects/domains/yourdomain/servers/yourserver/tmp

you can use the following commands to clear the cache:
WIN: rd C:\weblogic\user_projects\domains\yourdomain\servers\yourserver\tmp
UNIX: rm -rf /weblogic/user_projects/domains/yourdomain/servers/yourserver/tmp

Here I am removing all the subdirectories and files in the the given directory.

Question 30:

What is Thread dump?

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

Question 31:

When we will take Thread dump? Please give us some examples


Some of the examples would be
1.  when server is hang Position, i.e. that time server will not respond to coming requests.
2. While sever is taking more time to restart
3. When we are Getting exception like “java.lang.OutOfMemoryException”
4. Process running out of File descriptors. Server cannot accept further  requests because sockets cannot be created
5. Infinite Looping in the code

Question 32:

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 (like every 20mins, 5mins etc.).

Question 33:

What you Can Do with Node Manager

We can manage the whole gamut of activities from 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

Question 34:

How to check port number?

netstat -na |grep connected (to find the ports connected in Linux box.)
netstat -na |grep listen (to find the listening ports in HP-UX,Solaris)

Question 35:

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.

Question 36:

How can default JVM be changed to other?


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 domain for using the JRockit javac.exe
3) Remove any kind of switches specific to Sun JVM from start scripts of server.

Question 37:

What are the modes of operation for Weblogic server domains?


There are two modes
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.

Production mode:
You use production mode when your application is running in its final form. A production domain uses full security and may use clusters or other advanced features.

Question 38:

We see error  like  404 and 500. What does they mean?

The error code 404 – Page not found this says there is no page on the server when browser client requesting, this can happen when application is not deployed properly or not in active state or not initialized properly

500- Internal server error This error occurs when there is a communication issue between server’s intermediate services

Question 39: 

What is the difference between stage and no stage deployment?
Stage Deployment:- Admin server Having the physical copy and it will distribute to remaining instances.

Staged deployment will copy your deployment units onto the deployment servers, place them into the $WL_HOME/servers/SERVER_NAME/stage directory and deploy them from there.

In no-stage mode, the Administration Server does not copy the archive files from their source location. Instead, each target server must access the archive files from a single source directory for deployment. The staging directory of target servers is ignored for no-stage deployments.

Question 40:
how to Check the version of java in Unix ?

java -version run this command in linux to know the java version.