Weblogic Admin Interview Questions And Answers
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1. what’s Multicast and Unicast in WebLogic?
Answer: Multicast: Multicast is simpler to elucidate over Unicast. Multicast may be a broadcast UDP option for sending a packet/announcement over to a gaggle that’s listening on a selected multicast address and port over which the announcement is shipped .
There is an outlined range for valid Multicast address (224.0.0.1 to 239.255.255.255). Everyone listening on the given address hears the announcement a bit like following a Twitter post. Some limitations with Multicast is that the TTL (time to live) across machines/subnets/routers must be adjusted and therefore the routers configured to retransmit the multicast packet across subnets.
Unicast: Unicast is more of some extent to point UDP choice to send the packet to a selected member and not everyone. That way, unicast is more of a personal conversation between two individuals while multicast is more of a shout to a gaggle or room. Both are UDP based, so there are often losses, unlike TCP that handles retransmissions on message loss. But Unicast can span across routers and doesn’t need to worry about TTL without the everyone hearing the announcement. So, Network Admins, generally , like better to accompany Unicast over Multicast for these reasons.
2. How Does a Cluster Relate to a Domain?
Answer: A cluster is a component of a specific WebLogic Server domain. a website is an interrelated set of WebLogic Server resources that are managed as a unit. a website includes one or more WebLogic Server instances, which may be clustered, non-clustered, or a mixture of clustered and non-clustered instances. a website can include multiple clusters. a website also contains the appliance components deployed within the domain and therefore the refore the resources and services required by those application components and the server instances within the domain.
3. what’s The Admin Server?
Answer: Admin Server is that the central domain configuration interface which is employed to make , delete and configure the resources of a website like managed server, machine, cluster, data source, work managers, etc.
4. what’s a memory leak?
Answer: Memory leak is when objects aren’t faraway from the heap even once they aren’t required.
5. what’s A Stage Deployment?
Answer: Stage deployment may be a quite process during which the admin gets a physical copy which is distributed to the opposite instances.
6. what’s the Managed Server?
Answer: it’s an instance of your WebLogic server that’s running on JVM and has its own configuration. within the Managed server, we’ll deploy the java components Web Applications EJB Applications JMS Applications Web services.
7. what’s the Weblogic server?
Answer: Oracle WebLogic Server is J2EE Server (earlier referred to as BEA WebLogic Server) almost like Oracle Application Server. Oracle Weblogic server .
8. what’s Non-stage Deployment?
Answer: There’s no copy within the administrator but each and each server must contact the source directly for getting the item to be deployed.
9. What oracle WebLogic server includes?
Answer: Oracle WebLogic server includes 1)Domain 2)cluster 3)servers
10. What Are The Capabilities Of Weblogic Server?
Answer: There are various capabilities related to the WebLogic server and that they are Changes in dynamic configuration Production application redeployment Rolling upgrades
11. what’s Core Server Tuning?
Answer: This is the method involving the tuning of labor manager, chuck size, performance packs, chunk pool size, and connection backlog buffering.
12. How do you provide User credentials for starting the WebLogic server?
Answer: When you create a website , the Configuration Wizard prompts you to supply the username and password for an initial administrative user. If you want to create the domain in development mode, the wizard saves the username and encrypted password during a boot identity file.
A WebLogic Server instance can ask a boot identity file during its startup process. If a server instance doesn’t find such a file, it prompts you to enter credentials.
If you create a website in production mode, or if you would like to vary user credentials in an existing boot identity file, you’ll create a replacement boot identity file.
13. what’s the MSI mode in Weblogic? How are you able to 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 also be started in MSI mode if the Administration Server is unavailable. Configure MSI mode from the Administration Console.
To start a Managed Server in MSI mode, you have to follow these steps :
We have to Ensure that the Managed Server’s root directory carry the config subdirectory. If the config subdirectory doesn’t exist, copy it from the Administration Server’s root directory.
Start the Managed Server at the instruction or by employing a script.
Environment >> Servers >> Server_Name >> Tuning > > Advanced > > Managed Server Independence Enabled checkbox.
14. Difference between Weblogic Development and Production Mode?
Answer: Here we have some difference between Weblogic Development Mode and Production Mode:
Development Mode:
1) Sun Hotspot is the default JDK for development domain .
2) you’ll use the demo certificates for SSL
3) Auto deployment is enabled
4) On startup Server instances rotate their log files .
5) During startup Admin Server uses an automatically created boot.properties .
6) 15 is the default maximum capacity for JDBC Datasource.
Production Mode:
1) JRockit is the default JDK for production domain .
2) If you employ the demo certificates for SSL a warning is displayed
3) Auto deployment is disabled
4) when it reaches to 5MB Server instances rotate their log files .
5) During start-up Admin Server prompts for username and password .
6) 25 is the default maximum capacity for JDBC Datasource .
15. When we will take Thread dump? Please give us some examples?
Answer: Some of the examples would be
1. when the server is hung Position, i.e. that point server won’t answer coming requests.
2. While sever is taking longer to restart
3. once we are becoming exception like “java.lang.OutOfMemoryException”
4. A process running out of File descriptors. The server cannot accept further requests because sockets can’t be created
5. Infinite Looping within the code
16. what’s the Administration Server?
Answer: Admin server is that the central point from where you’ll configure, monitor and manage all resources of a website .
Administration Server is a WebLogic Server instance that maintains configuration data for a website .
You’ll post your application on the administration Server but it’s recommended to make managed Server and then deploy your application in managed server and leave Administration domain for configuration and maintenance.
There will always be a minimum of one Administration Server during a domain.
17. How do you differentiate a hang of a server and crash of server issue?
Answer: When a server crashes, the JAVA process not exists. When the server is hung, it stops responding.
So here We can use WebLogic.ADMIN practically to ping the server just in case of a hang situation, we will take multiple thread dumps and analyze the explanation for the hang.
18 Why the node manager is required?
Answer: A Node Manager process isn’t related to a selected WebLogic domain but with a machine. you will be using an equivalent Node Manager to regulate server instances , as long because the server instances reside on an equivalent machine because the Node Manager process.
Node Manager may be the must one to run on each computer that hosts WebLogic Server instances. whether Administration Server or Managed Server that you simply want to regulate with Node Manager.
19. How Can be notifications made when a server is added to a cluster?
Answer:
The WebLogic Server cluster broadcasts the supply of a replacement server instance whenever a new instance joins the cluster. Cluster-aware stubs also periodically update their list of obtainable server instances.
20. Tuning JVM Parameters?
Answer: If you’ve got one processor, the single-thread machine then you ought to use the serial collector (default for a few configurations, are often enabled explicitly for with -XX:+UseSerialGC).
For multiprocessor machines where your workload is essentially CPU bound, use the parallel collector. this is often enabled by default if you employ the -server flag otherwise you can enable it explicitly with -XX:+UseParallelGC. Keeping the GC which pauses shorter at the expense of using more total CPU time for GC, and you’ve got quite one CPU, you’ll use the concurrent collector (-XX:+UseConcMarkSweepGC).
The Parallel collector tends to know that they need some extra RAM which is already assigned to the JVM than the serial or parallel collectors for a given workload because some memory fragmentation can occur.
21. what’s the server?
Answer:
A server is an instance of WebLogic.Server executing during a Java Virtual Machine (JVM).
A server:
1) Runs on a delegated Oracle WebLogic Server machine
2) features a dedicated amount of RAM
3) Is multithreaded
Two sorts of servers:
1) Administration Server
2) Managed Server
22. what’s the Domain in Weblogic server?
Answer:
1) The domain may be a logically related group of Oracle WebLogic Server resources that are managed
as one unit
2) Domain Provides one point of administration
3) Can logically separate:
A) Development, test, and production applications
B) Organizational divisions
23. How managed servers communicate with each other?
Answer:
Managed servers communicate with one another using the t3 protocol internally.
24. How you Place your applications on Weblogic server?
Answer:
These are the kinds .
1) Auto Deployment
2) Console
3) Command-line – weblogic.deployer
4) ANT / WLST
25. What are often the explanations for Server hang?
Answer:
Memory leak, database query taking an extended time to return, Deadlock.
26. what percentage Weblogic Servers are often Held Inside A Multi-processor Machine?
Answer:
There are no limitations on Weblogic servers in Multi-Processor Machine.
27. In WebLogic Server what are the supported installation modes ?
Answer:
Graphical mode, console mode, and silent mode.
28. What are JVM Tuning Parameters?
Answer:
If you’ve got one processor, the single-thread machine then you ought to use the serial collector (default for a few configurations, are often enabled explicitly for with -XX: +UseSerialGC). For multiprocessor machines where your workload is essentially CPU bound, use the parallel collector. this is often enabled by default if you employ the -server flag otherwise 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’ve got quite one CPU, you’ll use the concurrent collector (-XX:+UseConcMarkSweepGC).
29. How does one do performance tuning of WLS? What are various areas to try to to it?
Answer:
a. Application Tuning.
JSP precompilation, EJB pool size cache.
b. OS Tuning
Setting the TCP IP parameter.
tcp_time_wait_interval
tcp_conn_req_max_q
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 pickup .
30. So How Could you start if the Managed Server in Administration server is in not available condition ?
Answer:
By default, during startup if Managed Server is unable to attach it can retrieve its configuration by reading a configuration file as well as some different files directly. You cannot change the server’s configuration until the Administration Server is out there . A Managed Server that starts during this way is running in Managed Server Independence mode.
31. what’s a website in WebLogic?
Answer:
The domain may be resources like admin server, managed server, JMS, connection pool, anyway of the resource you recognize of WebLogic server. since the domain is that the basic unit you’ve got to make after installation and everything created and configured under a website .
There can only be one administration Server within the domain and 0 to N Managed Server.
32. what’s asymmetric clustering in WebSphere?
Answer: Asymmetric clustering is well Reflection of the server farm where application is reflected across machines, and sometimes using distributed caching products for improving the performance.
In an asymmetric cluster, business logic is split into partitions, where each partition are often the only accessory of a group of underlying data .
This leads to each node within the cluster implementing its own local cache leading to high-performance reading and writing without the necessity to take care of a distributed cache between cluster nodes.
33. what’s WebSphere MQ JMS Provider?
Answer: IBM WebSphere MQ classes for Java Message Service are a group of Java classes that permits the JMS applications to access WebSphere MQ systems.
- Both point-to-point and publish/subscribe are supported.
- These Java classes are available as a part of the IBM WebSphere MQ client support.
34. We see a mistake like 404 and 500. What do they mean?
Answer: The error code 404 – Page not found this says there’s no page on the server when browser client requesting, this will happen when the appliance isn’t deployed properly or not in a lively state or not initialized properly
500- Internal server error This error occurs when there’s a communication issue between server’s intermediate services
35. What are often the varied reasons for a server crash?
Answer:
a) Native IO
b) SSL Native Libraries
c) JVM
d) Supported Configuration
e) JDBC Driver issue
36. How does one troubleshoot a crash?
Answer:
- JVM crash generates a hs_err_pid file. we’d like to seem into the stack trace of the hs_err_pid file.
- If the thread is from a native io, we’d like to disable native io.
- if the stack trace is from the driving force , we’d like to urge in-tuned with the drive team.
- Quite possibly its a drag with the driving force . Changing the sort of driver are often a workaround.
- If the thread shows it coming from an optimized code, we will close up optimization.
- If the stack is from native calls of application, its a bug with the appliance and it’s to b modified.
37. what’s the difference between stage and no stage deployment?
Answer:
Stage Deployment:- Admin server Having the physical copy and it’ll distribute to remaining instances.
The distribution will copy and paste them to deployment servers , $WL_HOME/servers/SERVER_NAME/stage directory and deploy them from there.
In no-stage mode, the Administration Server doesn’t copy the archive files from their source location. Instead of that , each and every targeted server should access the archive files from one source directory .
38. How can you Tyrn off the auto-deployment feature off?
Answer:
The auto-deployment feature checks the applications folder every three seconds to work out whether there are any new applications or any changes to existing applications then dynamically deploys these changes.
The auto-Distribution Mode is in Switch On Condition for servers that run in development mode.
To disable the auto-deployment feature, use one among the subsequent methods to put servers in production mode:
- =>In the Administration Console, click the name of the domain within the left pane, then select the assembly Mode checkbox within the right pane.
=>At the instruction , include the subsequent argument when starting the domain’s Administration Server:
- -WebLogic.ProductionModeEnabled=true
Production mode is about for all WebLogic Server instances during a given domain.
39. What happens when a failure occurs and therefore the stub cannot hook up with a WebLogic Server instance?
Answer: The stub removes the instance that’s failed from its list when a failure occurs. The stub uses DNS again for locating a running server and obtains a current list of instances when there are not any servers left in its list. The list of obtainable server instances within the cluster will get periodical refreshment, which allows making the advantage of latest servers. this is often because; the servers are added to the cluster.
40. what’s the boot?properties file? what’s the importance of it?
Answer: boot.properties is that the file employed 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 website in development mode then it creates automatically during startup of admin server but if you create a website in production mode then you would like to define it explicitly otherwise on every reboot of admin server it’ll prompt you for username and password.
So in production mode –
Quick Start the admin server by the passage 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 make a file “boot.properties” with below contents
username=your_admin_username
password=your_admin_password
Now start the admin server, it’ll not prompt you for username & password further. If you’re getting to start your managed servers from admin console then no got to create this file for the managed server but if you’re getting to start managed servers via start Managed weblogic script then you would like to follow an equivalent above procedure for everymanaged server.
41. what’s actually WebLogic Cache?
Answer: Casually the web-tier related files get stored in some directory. It is treated as cache when the restart of a WebLogic instance happen then the WebLogic server will look-up for last serviced object status stored within the cache to service for any pending requests.
Usually, in case u need EJB Classes need sessions, JMS object requires persistence, your web-tier may contain static contents then Cache are going to be employed by WebLogic Application Server instance.
42. Why should we got to remove Cache?
Answer: When your application is acquire for the primary time that fresh deployment of a replacement version, WebLogic server lookup during this directory if there are older objects persists which will be a conflict with new code objects.
This is often where the necessity for removal of cache arises. Where there’s a requirement of latest version deployment we’d got to clear the cache when the changes to the remake aren’t reflected.
Generally for WebLogic 9.x and better versions
WIN: C:weblogicuser_projectsdomainsyourdomainserversyourservertmp
UNIX: /Weblogic/user_projects/domains/your domain/servers/your server/tmp
you can use the subsequent commands to clear the cache:
WIN: rd C:weblogicuser_projectsdomainsyourdomainserversyourservertmp
UNIX: rm -rf /WebLogic/user_projects/domains/your domain/servers/your server/tmp
Here i’m removing all the subdirectories and files within the given directory.
43. what percentage sorts of WebLogic installation?
Answer:
There are 3 sorts of WebLogic installation.
(a) Graphical Mode (interactive GUI based)
(b) Console Mode (interactive Text Based)
(c) Silent Mode (Non-Interactive technique by using .xml properties file)
How to perform the WebLogic Installation
44. How does Cluster Communication Happen?
Answer: The Communication runs over the Cluster Multicast IP and Port by sending periodic heartbeat messages.
45. what’s the difference between the Sun JVM and BEA JRockit JVM?
Answer: The foremost well know JVM is that the implementation from Sun. The Sun JVM is named HotSpot. The Sun JVM is shipped within the Java Developer’s Kit and Java Runtime Environment from Sun.
The BEA JRockit JVM from the prefered BEA systems is improved for reliability and performance for server-side applications to realize this, BEA JRockit JVM uses technologies like code generation, hot spot detection, code optimization, advanced garbage pickup algorithms, and tight OS integration.
46. what’s HTTP tunneling? How can we configure it on WebLogic?
Answer: HTTP tuning is defined as how to simulate a tasteful socket connection between WebLogic Server and a Java client when your only option is to use the HTTP protocol. It generally wont to tunnel through an HTTP port during a security firewall. HTTP may be a stateless protocol, but WebLogic Server provides tunneling functionality to form the connection appear to be a daily T3Connection.
Steps to configure Http tunneling.
Login into the Admin Console, click on the server on which you would like to enable the Http Tunneling feature .
Click on the Protocols tab.
General check the “Enable Tunneling” checkbox.
Now you’ll communicate with the JVMs (Server Instances) using protocols aside.