Weblogic Interview Questions
1)Tell me about yourself?
2) Differences between 8.1,9.2 and 10.2,11g?
3)what are the daily Activities?
4)What are the regularly facing issues?
5)Server down/application not responding?
6)What are daily using UNIX commands?
7)What do you mean by connection pool? differences between connection pool and multipool?
8)What do you mean by data sources? differences between data sources and multi-data sources ?
9)Differences between Development and Production mode?
10)Jdbc and datasources configuration?
11) How to configure Apache proxy to weblogic?
12) How to configure IIs proxy to weblogic?
13)Weblogic deployment modes?
14)Differences between stage,no-stage and external stage mode?
15)what are imp files in weblogic?
16)What is MSI?
17)what is Node manager?different types of node managers?
18)What is cluster? how many types of clusters?
19)How we can achieve fail-over and load balancing in cluster?
20)what are the load balancing alogirthems?
21)Differences between Uni cast and Multicast?
22) How servers will communicate with in the cluster?
23)What is heartbeat?
25) what are the types of installation modes?
26)what silent.xml and silent mode installation?
27)what are the weblogic tuning parameters you know?
28)What is Permanent generation?
29)How to change deployment order?
30)what do you mean by deployment descriptor?
31)Differences between War and Ear?
32)Web server and application server?
33) what is weblogic server?
34)Side-by-side deployment?
35)Execute queues and work mangers?
36)How you take thread dump?
37)where thread dump will store ?what is the format of thread dump?
38)How analyze the thread dump? what are the threads you can see in thread dump?
39)what do you mean by Heap dump?
40)where it will store? what is the extension of heap dump? how you analyze heap dump?
41)what is core dump?
42)How you enable core dump? how you analyze core dump?
43) Differences between Thread dump,Heap dump and core dump?
44)What is T3 protocol?
45)what is Apache plugin module? how to check syntax error in appache?
46)How do you find Memory leaks in applications?
47)How DNS resolve the client request?
48) what do you mean by Ldap? did you configure ldap?
49)How to install and renew ssl certificates?
50) Do you know scripting ? how to write a script? what are all scripts used in your environment?
51)How to configure foreign JMS servers?
53)what is persistent store?
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1)How to check CPU usage?
2)How to check Memory in weblogic?
3)How do you invoke garbage collection?
4)how to check list of available port numbers?
5)how to increase the heap size?
6)how to increase the permgensize?
7)how to clear the weblogic cache?
8)how to check the disk usage?
9)what is ticketing tool?
Note: You can check my weblogic Material and weblogic troubleshooting issues for detailed explanation.
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Tell me about yourself?
Hi This is <Name>, I did my MCA in 2008 from Nagarjuna University.
Currently I am working with <Current working company>. Prior to that i have worked with <Previous company>
with the payroll of <if your working as contractor>
I involed in Installation of weblogic application server 8.1,9.2,10.3 I meant 11g and webserver
appache 2.0 and 2.2.
I have good experiance in Troubleshooting and Performance tuning as well as monitoring and
managing all weblogic server resources and webservices.
Apart from this,
1.I involued in creation and configuration of Domains.
2.Creation and configuration of clusters for providing load balencing and failover support.
3.Creation and configuration of JDBC and Datasources and connection pools.
4.Deployment of applications.
5.Managing SSL certificates.
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Day to day activities.
1.Taking shift handover from previous shifts.
2.Health status check-up of all weblogic server instances
Login to admin console and will check the all server status.
All server status should be running
If any of the server is failed kill those servers first.
Bounse or restart the server manually.
3.Checking the webservices and applications.
4.Periodical deployment on Non prod and production servers.
5.Supporing and following ITIL concepts in Incidents,change and problem management.
6.Providing on call support of 24*7 Basis.
7.Giving shift hand over to next shift.
________________________________________________________________________________
Working Environment
There are totaly 50 applications deployed on 10 domains.
Each domain contains of 1 horizantal cluster.
Each cluster contains 10-15 managed servers.
Currently we are working on Linux 4.0 and 5.0
Application server weblogic 9.2 and 11g
webserver Apache 2.0 and 2.2.
Backend DB is Oracle 9i.
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What is the difference between weblogic server 8.x/9.x/10.x?
| Weblogic 8 | Weblogic 9/10 |
| In WL 8.x we dont have LOCK & EDIT | Where as in WL 9/10 Lock and edit is the new feature |
| In WL 8.x we ahve execute queue’s | where as in WL 9&10 we are having workmanagers |
| In WL 8.x we have connection pools and data sources | where as in WL 9&10 we have only data sources and inside data sources we are having connection pools. |
| In WL 8.x you would need to delete and deploy the file again | In 9.x there is option to update an application that is deployed from the admin console. No need to un install and redeploy |
| In WL 8.x Side by side deployment is not possible | where as in WL 9.0 side-by side deployment is possible |
| In WL 8.x sever never comes-up if even one of the deployment fails | where as in WL 9.0 server gets into ADMIN mode |
| Diagnostic Framework is not there. | Diagnostic Framework” launch with wls10 and above |
| In Weblogic 8.x, all configuration and jms details will be present in the same config.xml |
whereas 9.x/10.x it will be partly maintained in config.xml and a separate xml files in domain/config/jms folders for each jms module. |
| In WL 8.x we don’t have config folder | Where as in WL 9/10 config folder is avilable |
| Console is an applet and uses JCX JCS JPF and Netui page flows | Console is portal and uses JSTL (JSP 2.0) |
| Persistent store is defined Under JMS | Persistent store is defined Under JDBC |
| No concept of JMS modules and sub deployments | Jms modules and subdeployments are included. |
| Queue/topic is configured under distributed destination | Queue/topic/dd etc are all clubbed in a JMS modules |
| In WL 8.x licence.bea file is present to update the licence | the difference is that there is a generic license.beafile for each version that you can downloand from oracle . No need to request a custom license.beafile. |
| In WL 8.x licence.bea file is present to update the licence | the difference is that there is a generic license.beafile for each version that you can downloand from oracle . No need to request a custom license.beafile. |
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Difference between web server and application server:
| Webserver
1) Which hosts websites. 2) Webserver is having web container can deploy war files. 3)webserver can effectively handle static contents. ex: Serverlet,jsps. 4) Webserver handles the HTTP protocol. When the Web server receives an HTTP request, it responds with an HTTP response, such as sending back an HTML page. 5) Web Server serves static HTML pages or gifs, jpegs, etc., and can also run code written in CGI, JSP etc.
|
Application Server 1)Which provides run-time environment to run J2EE applications. 2)Application server is having webcontainer as well as Ejb-container can deploy EAR files. 3)Application server can effectively handle dynamic content ex: EJB’S 4) Application server is more capable of dynamic behavior than webserver. We can also configure application server to work as a webserver. Simply application server is a superset of webserver. 5)Application Server supports distributed transaction and EJB. 6) An Application Server is used to run business logic or dynamically generated presentation code. It can either be .NET based or J2EE based |
Different between development mode and production mode
| Development mode
1)Auto deployment enabled 2) The default JDK for development domain is SunHotSopt.(SunJdk) 3) It is used demo certificate for SSL. 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 Date source is 15. 7) The debug flag which used to start the WebLogic workshop debugger is enabled. |
Production mode
1)Auto deployment is disabled. 2) The default JDK for production domain is JRocket. 3) It is used demo certificate for SSL a warning is displayed.
4) Server instances states their log files when it reaches 5Mb 5) Admin server prompt for username and password during startup. 6) The default maximum capacity for JDBC Date source is 25. 7) The debug flag which used to start the WebLogic workshop debugger is disabled. |
Differences between Unicast and multicast?
When servers are in a cluster, these member servers communicate with each other by sending heartbeats and indicating that they are alive. For this communication between the servers, either unicast or multicast messaging is used. This is chosen from the admin console in Cluster -> Configuration -> Messaging -> Messaging Mode.
To use multicast messaging, hardware configuration and support for multicast packets is required. Unicast does not have this requirement, which is why using unicast in latest versions is recommended.
When multicast messaging is used, it is a one-to-many communication, every server sends the notification/heartbeat/multicast packet to each other. This causes a heavy load on the application’s multicast buffer, so if the buffer is full, new multicast messages cannot be written to the buffer and the application is not notified when messages are dropped. So there is a possibility that the server instances miss the messages. This might lead in the cluster throwing out the server instances out of the cluster.
Unicast configuration is much easier because it does not require cross network configuration that multicast requires. Additionally, it reduces potential network errors that can occur from multicast address conflicts.
Mode of Communication:
Multicast – A multicast address and multicast port is used for listening to the messages.
Unicast – A network channel is used for communication between the servers. If no channel is specified, default network channel is used.
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Method of communication between servers:
Multicast – Each server communicates with every member server in the cluster. Which means heartbeats are sent to every server.
Unicast – For the member servers in the cluster, group leaders are chosen and only those group leaders communicate with the servers among the group and these leaders notify each other about the availability of all the other servers.
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For new server versions, using unicast is recommended because it is a simplified communication mode. But for backward compatibility with the previous versions, you will need to use multicast if there is a communication requirement between clusters of versions prior to WLS 10.0.
Diff b/w Xa and Non-Xa Datasource ?
| Xa datasource
1) It allows global transaction that my be multiple resources. 2) It involves a co-ordinating transaction manager with one or more databases in a single global transaction. 3) It comes from the X/Open group specification on distributed, global transactions. |
Non-Xa Datasource
1) It allows single transaction that my be single resources. 2) there is no transaction coordinator, and it is a single resource is doing all its transaction work itself. 3) It comes from Servlet or EJB or plain old JDBC in a Java application talking to a single database. |
Table of Deployable Modules and Deployment modes.
| Application or Module | Archive Extension | Key J2EE Deployment Descriptor |
| Enterprise Application | .ear | META-INF/application.xml |
| Enterprise JavaBean Module | .jar | META-INF/ejb-jar.xml |
| Web Application | .war | WEB-INF/web.xml |
| Web Service | .ear or .war | WEB_INF/web-services.xml |
| Connector Module | .rar | META-INF/ra.xml |
| Startup or Shutdown Class | n/a | No deployment descriptor (Class file only) |
Unix commands Interview questions
unix commands :-
1.Search a file from root directory.(filename = sample.txt)
find / -name sample.txt
2.Display the numbers in sorted order
sort -nu
3.Display the updated lines in file
tail -f filename
4.How to zip a Directory
gzip -r /hom/bea/app
5.How to kill a prosess.
kill -9 pid
6.Display all java process in unix.
ps -ef |grep java
7.How to delete 10 lines in vi editor.
10dd
8.How to search a string and replace tin vi editor.
:”%s/old string /new string/ gi”
9.How to search a string in vi editor from bottom to top.
?string name
10.How to insert a line above the current line in vi editor .
esc+o
11.How to rename a file .
mv file1 file2
- copy the content one directory to another directory.
cp -r dir1/file1 dir2/file2
- How can delete blank lines in directory.
grep -v “^$” sample > temp
mv temp sample
14.How can replace astring in unix.
sed “s/oldstring/newstring/g” filename
15.Syntax for zip and unzip afile.
gzip filename
guzip filename.gz
16.How can display top 10 disk usage files.
du -sh *|sort -nr|head -10
17.How to retrive a field in a file.
cut -f 1,2 stud.
18.what is command search a string in a file.
grep
19).How to goto the end of the line in Vieditor?
G
20).Copy 10 line in vi editor?
10yy
21).How to go to insert mode in vi editor?
Esc+i
22).How to search a string in a file(filename=sample,string=weblogic)?
grep weblogic sample
23).How to copyfile from one unix to other unix system and syntax (file=sample.txt,target host=192.168.11.128,target file path=/home/bea)?
scp -rp sample.txt username@192.168.11.128:/home/bea
24).Copy file from path to other tree structure is given below?
25).How to find out CPU utiligation?
top
26).How to execute ascript using nohup(script name=startweblogic.sh)?
nohup ./startWeblogic.sh &
27).Which command is used to search and replace a string?
sed
28).wich command is used to search astring in multiple files?
fgrep
1)How to search a string from top to bottom in vi Editor’s(String =weblogic)?
- A) /weblogic
2)how to save and quit from vi Editor’s?
a)WQ!
3)what are the Advantages of nohup command?
A)nohup will execute the process if you layout system.
Syn:nohup &.
4)Differance b/w the ping and tracert?
- A) ping tracert
1)It is check the connectivity. 1.It is packet information one place to
another place destination.
2)It is display all at a time. 2.It display only 30 hubs in tracert.
5)How to execute unix commands in vi?
A):ls
6)tar dir1 dir2 dir3 and new_dir?
A)syn:tar -cvf new_dir.tar dir1 dir2 dir3.
7)How to display the ipaddress and portnumber?
A)netstat -anp
8)how to delete directory with recursion and force?
A)rm -rf filename.
9)How to Open a file with page to page ?
A)more filename
10)How to Hide a file (file name=tuxedo)?
A)mv tuxedo .tuxedo
11)How to do undo in vi Editor’s?
A)u
12)How to goto 100 Line in Vi Editor’s?
A)100L
13)How to display last 100 Line from a file?
A)tail -100 filename
14)How to Reterive the fields from a file?
A)cut
15)How to zip a directory?(/home/directory)?
A)gzip -r /home/directory
16)How to go to end of the line in Vi?
A)G
17)Display the directiory count in current dir?
A)ls -lrt !wc -l
18)How to display all files ending with “log”?
19)How to appeand data to the existing file?
A)cat>>filename
20)How to find out the diskspace of the fileSystem?
A)df -sh
21)write A syntax for the scp Commands?
- A) Scp filename root@ipaddress:filename.
22)How to display the updated lines in file ?
A)tail -f filename.
23)How to display the ipaddress and portnumber?
A)netstat -anp
24)which command is used to connect to the remote server?
A)telenet ipaddress.
25)How to repalce and String in vi Editor’s?
- A) sed %s/oldstring/newstring/g
25)How to repalce and String in unix?
- A) sed s/oldstring/newstring/g filename
26)How to display top 10 lines from a file?
- A) head -10 filename.
27)syntax for tar and untar a file?
A)tar -cvf filename.tar file1 file2 file3.
tar -Xvf filename.tar
28)How to display hiddean a file?
A)ls -a.
29)How to Delete a blank line from a filename?
A)grep “^v” sample >temp
mv temp filename
30)How to display all cuurent running process?
A)ps -ef
31)syntax for zip and unzip file?
A)gzip filename.
gunzip filename.gz
1. 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.
2. 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
3. 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 optimzed 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.
4. 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.
5. What can be the reasons of Server hang?
Memory leak, databse query taking a long time to return, Deadlock.
6. What is memory leak?
Memory leak is when objects are not romved from the heap even when they are not required.
7. What are the various causes for OUT OF MEMORY?
a) Insufficient heap size, not able to match the extra load.
b) Objects licing too long, like HTTP Sessions.
c) Memory leak in application code.
d) Full GC not happening due to JVM Bug.
8. 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.
9. When does High CPU Usage occur?
It occurs when one process or one thread utilizes unexpectedly high proportion of CPU.
10. 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.
11. What is Clustering and what is achieved through it?
Clustering is the grouping together of servers for the purpose of high availability and scalability.
Load balancing and Failover is achieved.
12. How does Cluster Communication Happen?
Members of the Cluster communicate over the Cluster Multicast IP and Port by sending periodic heart beat messages.
13. 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.
14. TUning JVM 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). 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.
15. How do you do performance tuning of WLS?
It can be categorized in 4 parts.
a. Application Tuning.
jsp precompilation, ejb pool size cache..
b. OS Tuning
Setting tcp ip parameter.
tcp_time_wait_interval
tcp_conn_req_max_q
c. Core Server Tuning.
tune workmanager, tune chuck size and chunck pool size, using performance packs, conenction backlog buffering.
d. JVM Tuning
tuning gc strategy, monitoring garbage collection..
16. What is the difference between Development mode and Production mode of Weblogic Server?
Development Mode:
1. The default JDK for development domain is Sun Hotspot.
2. You can use the demo certificates for SSL.
3. Auto deployment(to admin server only) is enabled.
4. Server instances rotate their log files on start-up.
5. Admin Server uses an automatically created boot.properties during start-up.
6. The default maximum capacity for JDBC Datasource is 15.
7. The debugFlag which is used to start the WebLogic Workshop Debugger is enabled.
8. In Development Mode any configuration change being done by a user doesn’t need him to take a Lock and Edit session.
9. Availability of web service test client.
10. Nodemanger username and password: Default Admin credentials.
11. Availability of Classloader Analysis Tool: Yes.
12. Default start parameters when using Sun JDK and the default startWebLogic script : java -client -Xms256m -Xmx512m -XX:CompileThreshold=8000 -XX:PermSize=128m -XX:MaxPermSize=256m.
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(to admin server only) is disabled.
4. Server instances rotate their log files when it reaches 5MB.
5. Admin Server prompts for username and password during start-up.
6. The default maximum capacity for JDBC Datasource is 25.
7. The debugFlag which is used to start the WebLogic Workshop Debugger is disabled.
8. In Production Mode the user needs to procure a Lock and Edit session before trying to make any configurational changes.
9. No Availability of web service test client.
10. Nodemanger username and password: Randomly generated
11. Availability of Classloader Analysis Tool: No.
12. Default start parameters when using Sun JDK and the default startWebLogic script : java -server -Xms256m -Xmx512m -XX:MaxPermSize=256m.
Ref :- http://impradeep.com/difference-between-production-and-development-mode-in-weblogic/
17. What is HTTP tunneling? How can we configure it on Weblogic?
HTTP tunneling provides a way to simulate a stateful 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 ? General ? check the “Enable Tunneling” check box.
Now you can communicate with the JVMs (Server Instances) using protocols other than t3
18. 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’s 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.
19. What is work managers ?
Weblogic server allows you to configure, how your application prioritizes the execution of it’s work. Based on rules and constraints you can define how WebLogic Server prioritizes work and allocates threads based on an execution model that takes into account administrator-defined parameters and actual run-time performance and throughput.
Workmanager applying it either globally or to a specific application component.
1.Default work managers: WLS implements a default workmanager when no-other work managers are specified.
2.Global work manager: Global work managers are created in weblogic administrative console and are defined in config.xml it is created as template.
3.Application scoped work managers: Work managers available only to a specific application (or) module.
Work Managers can be configured at the
3.1.domain level
3.2.application level
3.3. module level
in one of the following configuration files:
config.xml—Work Managers specified in config.xml can be assigned to any application,
or application component, in the domain. You can use the Administration Console to define a Work Manager.
weblogic-application.xml—Work Managers specified at the application level can be assigned to that application, or any component of that application.
weblogic-ejb-jar.xml or weblogic.xml—Work Managers specified at the component-level can be assigned to that component.
weblogic.xml—Work Managers specified for a Web Application.
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