Weblogic Basic Interview Questions

1. What is Weblogic?

Weblogic is a server software application that runs on a middle-tier between the Database and related applications and browser-based thin clients.
Weblogic is a leading e-commerce online transaction processing (OLTP) developed to connect users in a distributed computing environment and to facilitate the integration of mainframe applications with distributed corporate data and applications.

2. What is Administration Server?
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 server for configuration and maintenance. In weblogic, each domain will have one Administration Server and Multiple Manage servers.

3. What is Managed server?
Any weblogic server instance apart from administration server is called as Managed servers.
Though you can deploy your application in Administration server as well but it is not recommended in production/UAT instance. so, you can deploy your application in Managed server for high availability.

4. What is Node Manager?
Node manager is a weblogic server utility that enables you to start, shut down, and restart administration server and managed server instances from a remote location (weblogic console).
There are two types of Node manager . 1)Java-Based Node manager 2)Script-Based Node manager.
Java-Based Node manager:Java-based Node manager runs within a Java Virtual Machine (JVM) process.
It is recommended that you run it as a Windows server and VBox UNIX platforms.
Script-Based Node manager:For UNIX and Linux systems, Weblogic Server provides a script-based version of Node manager.

5. What are the Important configuration files in Node Manager?
The following are the important configuration files is Node manager. 
Nodemanager.properties:This is the configuration file used by the Java-based version of Node manager.
This file is located in WL_HOME/common/nodemanager.
startup.properties:Each Managed server instance has its own startup.properties file with properties that control how           Nodemanager starts up and controls the server.
Nodemanager automatically creates this file by using properties passed to Nodemanager when the

Administration Server was last used to start the server.
This allows a Nodemanager client or startup scripts to restart a Managed server using the same

properties last used by the Administration Server.
Nodemanager.domains:This file contains mappings between the names of domains managed by Nodemanager and their corresponding directories.
This file is located in WL_HOME/common/nodemanager.
nm_data.properties:This file stores the encryption data the Nodemanager uses as a symmetric encryption key.
This file is located in WL_HOME/common/nodemanager.
nm_password.properties:This file stores the Nodemanager username and password.
This file is located in DOMAIN_HOME/config/nodemanager.
boot.properties:Nodemanager uses this file to specify user credentials when starting a server.
This file is located in DOMAIN_HOME/servers/server_name/data/nodemanager.

6. What is Cluster in Weblogic ?
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.

7.What are the prerequisits for webloic installation?
Selected OS(Including RPM's), JDK and Weblogic software.

8.What are the prerequisits for installing database for weblogic ?
      character set              :  AL32UTF8 character set
      Shared Pool Size        : 144 MB
      SGA Maximum Size   : 144MB
      Block Size                 : 8KB
      Processes                  : 500

9. What is Garbage collection?
Garbage collection (GC) is a form of automatic memory management. The garbage collector attempts to reclaim garbage, or memory occupied by objects that are no longer in use by the program.

10. How to Increasing JVM Size (heap size) of Admin Server?
JVM size of Admin server can be increased by changing Xmx and Xms  values in setDomainEnv.sh
which is located in $MW_HOME/user_projects/domains/base_domain/bin
11. What is RCU? why we are Installing RCU?
RCU is Repository creation utility. RCU provides the flexibility to create custom schemas and tablespaces in databse. You can choose to rename schemas, or change the tablespace allocation so that components can share a single or multiple tablespaces. In addition, auxiliary schemas can be mapped to additional tablespaces.

12.Difference between the production mode and development mode in Weblogic server?

Development Mode:

  ü  The Default JDK for development domain is Sun jdk.

  ü  you can use the demo certificates for SSL.

  ü  Auto deployment is enabled.

  ü  server instances rotate their log files on startup.

  ü  Admin server uses an automatically created boot. Properties during startup.

  ü  The default maximum capacity for JDBC Data source is 15.

Production Mode:

  ü  The default JDK for production domain is JRocket.

  ü  If you use the demo certificate for SSL a warning is displayed.

  ü  Auto deployment is disabled.

  ü  server instance rotate their log files when it reaches 5MB.

  ü  Admin server prompts for username and password during startup.

  ü  The default maximum capacity for JDBC Data source is 25.

13. What is Domain?

Domain is a collection of logical grouping of resources and services and consist of Administration server, Managed server and cluster. There can only be one admin server and zero-n Managed servers in domain. These total domain information is stored in config.xml file.

14. What is config.xml file?

  ü  This file specifies the configuration of each server instance, cluster, resource and services in the domain. This file located in MW_HOME/user_projects/domains/doamin_name/config/config.xml(DOMAIN_HOME/config/config.xml).

  ü  Each time the Administration server starts successfully, a backup configuration file config.xml booted file is created in domain directory.

15.How many modes of Installation of Weblogic server?

There are Three modes of Installations of Weblogic server.

  ü  Graphical Mode:

 Windows>double click on .exe file.

Unix > chmod a+x filename.bin /filename.bin;

  ü  Console Mode:

Windows>WLServerXXX_win32.exe -mode=console

Unix> chmod a+x filename.bin /filename.bin -mode=console;

  ü  Silent Mode:

Windows> WLServerXXX_win32.exe -mode=silent -silent_xml=path_of_silent.xml

Unix>chmod a+x filename.bin -mode=silent -silent_xml=/path_to_silent.xml -log=/home/logs/ platform_install.log;

16. How many ways to startup the Weblogic server?

Weblogic server can be started in the following ways:

  ü  startWeblogic.sh

  ü  Using WLST and ANT scripts.

  ü  Node manager

ü  Weblogic.Admin start command

17. How many types of clustering are there in Weblogic server?

There are Two types of clustering:

1.Vertical clustering.

2.Horizontal clustering.

Vertical clustering:

Group of available weblogic server instances in a single physical machine as cluster is called vertical cluster.

Horizontal clustering:

Grouping of multiple application servers that are run on two or more different physical machines is called Horizontal clustering. It is more reliable than vertical clustering.

In Real Time: Basic Tier cluster with horizontal mc1, mc2.

18.How Weblogic server instance methods to communicate in a cluster and how server detect failure?

Weblogic server instance in a cluster communicate with the following Network technologies:

1)Sockets Communication

2)Heart Beat Communication

Socket Communication:

(one to one or peer to peer) each server instance will communicate with IP socket programming for sharing the information.

Heart Beat Communication:

each server will communicate with the cluster by sending the heart beat for every 10 sec. If does not receive a heart beat from the server for 30 seconds or longer, the monitoring server makes the peer server as "failed".

There are two types of Messaging modes for external communication systems:

1)Unicast Messaging Mode

2)Multicast Messaging Mode

Unicast  Messaging Mode:

Here we have three servers (MS-1,MS-2,MS-3) in a cluster now if they have to communicate with each other            they have to ping (i.e. heartbeats ) the cluster master for informing him that he is alive.

If MS-1 is the master then MS-2 and MS-3 would send the ping to MS-1

Multicast Messaging Mode:

Here there is no cluster master each server has to ping each other to inform everyone that I am alive.

So MS-1 would send the ping to MS-2 & MS-3 same way MS-2 would send the ping to MS-1 & MS-3 and MS-3

would ping MS-1 & MS-3.

Thus if you see in multicast the congestion in sending the pings are more compared to unicast which makes

 multicast much heavier, thus WLS recommends using Unicast of less congestion in the network.

(congestion=overcrowding)

 19. What are the Different states of Server Lifecycle?

Starting state:

When we issue any type of startup command the server instance transitions from the SHUTDOWN to the STANDBY state. During the STARTING state the instance reads the domain configuration data from its config directory, whereas the Managed Servers will get their configuration data from the Admin Server.

Standby state:

During this state all ports are closed, but you can quickly transition to a RUNNING state from here, so this state could be used to keep a server in a hot STANDBY mode.

Admin state:

The ADMIN state permits only administrative tasks such as deploying applications, with those applications being able to process only requests from users with the Admin and AppTester roles.

Resuming state:

This is a purely transitional state the server instance goes through after it transitions automatically through the ADMIN state or you issue the resume command after first placing the instance in the STANDBY or ADMIN state.

Running state:

During the RUNNING state that the server can accept and service client requests for its services.

20. What is WLST?

The Weblogic Scripting Tool (WLST) is a command-line scripting interface that system administrators and operators use to monitor and manage Weblogic Server instances and domains. The WLST scripting environment is based on the Java scripting interpreter, Jython(pure java implementation of python).

Command for Invoking WLST:java>bin>java weblogic.WLST  c:\myscript.py

There are Two types of connection modes:

1)Offline Mode:

WLST helps you to create and extend a domain, and  create domain templates. In offline mode, WLST acts as an interface to the Node Manager and you can issue WLST commands to start and stop Managed Server instances without connecting to the Admin Server.

2)Online Mode:

WLST in online mode acts as a Java Management Extensions (JMX) client that manages the domain’s resources by modifying the server’s Configuration MBeans. Thus, WLST offers you all the domain management configuration capabilities as the Administration Console.