Weblogic Admin Interview Questions And Answers

1. What is Multicast and Unicast in WebLogic?
Multicast: Multicast is easier to explain over Unicast. Multicast is a broadcast UDP option for sending a
packet/announcement over to a group that is listening on a specific multicast address and port over
which the announcement is sent.

There is a defined range for valid Multicast address ( to Everyone listening on the given address hears the announcement just like following a
Twitter post. Some limitations with Multicast is the TTL (time to live) across machines/subnets/routers
needs to be adjusted and the routers configured to retransmit the multicast packet across subnets

Unicast: Unicast is more of a point to point UDP option to send the packet to a specific member and not everyone.
That way, unicast is more of a private conversation between two individuals while multicast is more of a
shout to a group or room. Both are UDP based, so there can be losses, unlike TCP that handles
retransmissions on message loss. But Unicast can span across routers and does not have to worry about
TTL without the everyone hearing the announcement. So, Network Admins, in general, prefer to go with
Unicast over Multicast for these reasons.

2. How Does a Cluster Relate to a Domain?
Answer: A cluster is part of a particular WebLogic Server domain. A domain is an interrelated set of
WebLogic Server resources that are managed as a unit. A domain includes one or more WebLogic Server
instances, which can be clustered, non-clustered, or a combination of clustered and non-clustered
instances. A domain can include multiple clusters. A domain also contains the application components
deployed in the domain and the resources and services required by those application components and
the server instances in the domain. (E learning Portal)

3. What Is The Admin Server?
Answer: Admin Server is the central domain configuration interface which is used to create, delete and configure the resources of a domain like managed server, machine, cluster, data source, work managers, etc.

4. What is a memory leak?
Answer: Memory leak is when objects are not removed from the heap even when they are not required.

5. What Is A Stage Deployment?
Answer: Stage deployment is a kind of process in which the admin gets a physical copy which is distributed to the other instances. (E learning Portal)

6. What is the Managed Server?
It is an instance of your WebLogic server that is running on JVM and has its own configuration.
In the Managed server, we will deploy the java components
Web Applications
EJB Applications
JMS Applications
Web services

7. What is the Weblogic server?
Answer: Oracle WebLogic Server is J2EE Server (earlier known as BEA WebLogic Server) similar to Oracle Application Server.
Oracle Weblogic server

8. What Is Non-stage Deployment?
Answer: There is no copy in the administrator but each and every server needs to contact the source directly for getting the item to be deployed.

9. What oracle WebLogic server includes?
Oracle WebLogic server includes

10. What Are The Capabilities Of Weblogic Server?
There are various capabilities associated with the WebLogic server and they are
Changes in dynamic configuration
Production application redeployment
Rolling upgrades

11. 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.

12. How to access the admin console?
SSL enabled admin console accessed as :
or IP address (where admin server running):(port on which admin server is SSL
enabled admin console accessed as :
nonsense admin console accessed as :
or IP address (where admin server running):(port on which admin server is SSL enabled
admin console accessed as:
13. How do I provide User credentials for starting the WebLogic server?
When you create a domain, the Configuration Wizard prompts you to provide the username
and password for an initial administrative user. If you create the domain in development mode, the
wizard saves the username and encrypted password in a boot identity file. A WebLogic Server instance
can refer to a boot identity file during its startup process. If a server instance does not find such a file, it
prompts you to enter credentials.
If you create a domain in production mode, or if you want to change user credentials in an existing boot
identity file, you can create a new boot identity file.

14. What is the MSI mode in Weblogic? How can you enable and disable this option?
Answer: MSI is nothing but Managed Server Independence. By default, Managed Servers can function
independently of the Administration Server. A Managed Server instance can start in MSI mode if the
Administration Server is unavailable. Configure MSI mode from the Administration Console.
To start a Managed Server in MSI mode, perform the following:
Ensure that the Managed Server’s root directory contains the config subdirectory. If the config
subdirectory does not exist, copy it from the Administration Server’s root directory.
Start the Managed Server at the command line or by using a script.
Environment > Servers > Server_Name > Tuning > Advanced > Managed Server Independence Enabled

15. Difference between Weblogic Development and Production Mode?
Here are some difference between Weblogic Development Mode and Production Mode:
Development Mode:
1) The default JDK for development domain is Sun Hotspot
2) You can use the demo certificates for SSL
3) Auto deployment is enabled
4) Server instances rotate their log files on startup
5) Admin Server uses an automatically created boot.properties during startup
6) The default maximum capacity for JDBC Datasource is 15
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 is disabled
4) Server instances rotate their log files when it reaches 5MB
5) Admin Server prompts for username and password during startup
6) The default maximum capacity for JDBC Datasource is 25

16. When we will take Thread dump? Please give us some examples?
Some of the examples would be
1. when the server is hung 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. A process running out of File descriptors. The server cannot accept further requests because sockets cannot be created
5. Infinite Looping in the code

17. What is Cluster in WebLogic?
Answer: 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 within-cluster can run on the same machine or different machines. These are also called a managed Server cluster.

18. What is the Administration Server?
Answer: Admin server is the central point from where you can configure, monitor and manage all resources of a domain.
Administration Server is a 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.

19. How do you differentiate between a server hang and server crash issue?
Answer: When a server crashes, the JAVA process no longer exists. When the server is hung, it stops
We can use WebLogic.ADMIN utility to ping the server. In case of a hang situation, we can take
multiple thread dumps and analyze the cause of the hang.

20. Why the node manager is required?
Answer: 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.

21. How are notifications made when a server is added to a cluster?
The WebLogic Server cluster broadcasts the availability of a new server instance each time a
new instance joins the cluster. Cluster-aware stubs also periodically update their list of available server

22. Tuning JVM Parameters?
Answer: If you have a single processor, the 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). Note that the concurrent collector tends to require more RAM allocated to the JVM than the serial or parallel collectors for a given workload because some memory fragmentation can occur.

23. What is the server?
A server is an instance of WebLogic.Server executing in a Java Virtual Machine (JVM).
A server:
1) Runs on a designated Oracle WebLogic Server machine
2) Has a dedicated amount of RAM
3) Is multithreaded
Two types of servers:
1) Administration Server
2) Managed Server

24. What is the Domain in Weblogic server?
1) The domain is a logically related group of Oracle WebLogic Server resources that are managed
as a single unit
2) Domain Provides one point of administration
3) Can logically separate:
A) Development, test, and production applications
B) Organizational divisions

25. How managed servers communicate with each other?
Managed servers communicate with each other using the t3 protocol internally.

26. How you deploy your applications on Weblogic server?
These are the types.
1) Auto Deployment
2) Console
3) Command-line – weblogic.deployer

27. What can be the reasons for Server hang?
Memory leak, database query taking a long time to return, Deadlock.

28. How Many Weblogic Servers Can Be Held Inside A Multi-processor Machine?
There is no limitation on the number of servers.

29. What are the supported installation modes for WebLogic Server?
Graphical mode, console mode, and silent mode.

30. What are JVM Tuning Parameters?
If you have a single processor, the 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).

31. 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 the 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.

32. Can I 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.

33. What is a domain in WebLogic?
The 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 the 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 the domain and zero to N Managed Server.

34. What is asymmetric clustering in WebSphere?
Answer: Asymmetric clustering architecture is opposite to the typical stateless server farm where the entire app is replicated across machines, sometimes using distributed caching products for improving the performance.
In an asymmetric cluster, business logic is split into partitions, where each partition can be the sole accessory of a set of underlying data
This results in each node in the cluster implementing its own local cache resulting in high-performance reading and writing without the need to maintain a distributed cache between cluster nodes.

35. What is WebSphere MQ JMS Provider?
Answer: IBM WebSphere MQ classes for Java Message Service are a set of Java classes that enables the JMS applications to access WebSphere MQ systems.
Both the point-to-point and publish/subscribe models of JMS are supported.
These Java classes are available as part of the IBM WebSphere MQ client support.

36. We see an error like 404 and 500. What do they mean?
Answer: The error code 404 – Page not found this says there is no page on the server when browser client requesting, this can happen when the application is not deployed properly or not in an active state or not initialized properly
500- Internal server error This error occurs when there is a communication issue between server’s intermediate services

37. What can be the various reasons for a server crash?
a) Native IO
b) SSL Native Libraries
c) JVM
d) Supported Configuration
e) JDBC Driver issue

38. 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 the driver. Changing the type of driver can be a workaround.
If the thread shows it coming from an optimized code, we can turn off optimization.
If the stack is from native calls of application, its a bug with the application and it has to b modified.

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.
The 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.

40. 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 the auto-deployment feature, use one of the following methods to place servers in production
=>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
Production mode is set for all WebLogic Server instances in a given domain.

41. 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.

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

43. What is actually WebLogic Cache?
Answer: 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 the 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 persistence, your web-tier may contain static contents then Cache will be used by WebLogic Application Server instance

44. Why do we need to remove Cache?
Answer: 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 a conflict with new code objects. This is where the need for 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 are 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/your domain/servers/your server/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/your domain/servers/your server/tmp
Here I am removing all the subdirectories and files in the given directory.

45. How many types of WebLogic installation?
There are 3 types of WebLogic installation.
(a) Graphical 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

46. How does Cluster Communication Happen?
Answer: Members of the Cluster communicate over the Cluster Multicast IP and Port by sending periodic heartbeat messages.

47. What is the difference between the Sun JVM and BEA JRockit JVM?
Answer: 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.

48. What is HTTP tunneling? How can we configure it on WebLogic?
Answer: 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 the Http Tunneling feature
Click on the Protocols tab
check the “Enable Tunneling” checkbox.
Now you can communicate with the JVMs (Server Instances) using protocols other than t3.

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