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WebLogic Administrator interview questions 4



1. When do we go for jdrivers and  XA drivers?Advantages?


This question is focused for weblogic Architect/developers. This choice is depends on the application if it is having more transaction with Database requires reliable connections with the DB, more Entity Beans on the ejb-tier then we need to choose JDriver when JDO is in application side. Transactional consistency is mandatory for the application and response time is no matter then we choose XA.

 

2. Is there any disadvantages of using machines in cluster configuration?

Yes, If Weblogic domain not using the feature of NodeManager then it is a useless configuration.

 

 

3. What happens if we delete the log files when the server is running & when the  server is not running?

Better option is to NULLify the content of the log after archiving the logs. Nothing  happen when we delete a WebLogic server log files, When server is RUNNING, new logs will be generated w.r.t Server instance and application logs depends on log4j.properties.

New loggging will be written if the file exists. It will always do appending to the log file. If the file is removed then no appending happens. So that you don't know what is happening to the Server instance. The other case, When NOT RUNNING not new log generated :)

 

4. Can we change the name of the log files?

When we want to change the log file names while running. If we change at run time WebLogic will creates new log file again.

Using WLST, specifying logger with edit, save we can change it in the domain level also. Ref: Unnikrishnan pillai blog.

 

5. What is the actual procedure of the application deployment in realtime? Basic  reqiurement?

If there is no deployment tools in use then no-stage mode is preferred for production. Application code will be deployed when target managed server is restarted. Admin server need not to copy the code to remote machine. But you need to place the code in the code directory. 


Production Redeployment can be done with weblogic.Deployer command also. 


Latest version prefers to use deployment plan. 


Realtime in the sense development or in Production? If it is Development procedure is simple we can use hot deployment.

the number of components of the application are scheduled in sequance of deployment order.

for entity-ejbs some times requires restart of the server.


 

6. Why datasources ,JMS  need JNDI?

JNDI is a light weight directory which is used to lookup from other resources. Entity EJB lookup for DataSource, Message Driven

Beans lookup for JMS. Servlets, JSP web compoents lookup for JDBC connections for few actions. which is not recommmend in real time.

 

7.Benefits of  jRockit over jdk?

JRockit JVM strongly built with Aspect of Programming, POJO

JRockt don't have separate class loading in JVM space. Sun JDK JVM have a dedicated memory space for it, that is PermSize.

JRockit performance is good once it is in RUNNING. 

Sun JDK is faster than JRockit at launching time. 

GC options are varies in both.

Please visit: http;//wlabypani.blogspot.com

 

8.What is Bootup Process?

StartWebLogic.sh script flow need to explain...

CLASSPATH 

MEMARGS

GC parameters

to start the weblogic.Server class

check authentication if user, password given script takes from it. if not

check for boot.properties


Domain bootup process is like this...

Admin Server -> EJB TIER servers -> Web - Tier

 

9. How do u  identify weblogic health in production?

Main Threads...

checking ThreadPool state for the WebLogic instance. 


This depends on the client capacity ... if Client is willing to spend much on monitoring no downtime then Introscope,

HP-OVO some more tools are available. for me I m using WLST for JVM, Idle, Hogging thread count program which I had published in my blog.

 

10. What are the action to be taken when server is crash ?core file  is not genetated what to do?

if sever is crash u cannot do anything after words :) if u got alerts you can managed to get Heapdumps as you told.

reason pstack, jmap, pmap requires process id.

If third party package installed in Solaris then you can use dbx command for further investigation.

In solaries  we use pstack and pmap command to take long stack and to find which thread  library causes the problem instead of  using debbuger.. For linux is there any command that do the same tasks..pmap is working in linux but there is no pstack command..after a long search i found one command which is equal to pstack ...i.e  lsstack ( equal to pstack)..  but it is not working...

 

11. Difference between Weblogic previous 8.1 and  9.2 above versions such as ,10.3?

This you can ans only when you read release notes of each one.

already given weblogic interview questions 3


WLS Management from 6.0 to 8.1

WLS Management from 9.0 & above

Proprietary Remotable APIs to access MBeanServer

Standards based, JSR 160. Deprecated MBeanHome & RemoteMBeanServer

One MBeanServer, hosted all MBeans

4 MBeanServers, each MBS hosts MBeans depending on functionality

Non schema based config.xml

Schema based config.xml

Many broken links in MBean hierarchy

All MBeans completely Linked, making the hierarchy traversable

MBeanHome - Factory for creation/deletion of all MBeans

Each parent MBean serves as a Factory to create/delete its Child MBeans

Configuration change mechanism is atomic

Introduction of transaction semantics to configuration change

No control over configuration changes and often unpredictable

Need a lock on configuration to make a change, more control (can undo changes, stop edits etc)

AdminMBeanHome provided the federated view of the Domain

DomainRuntime MBeanServer provides the federated view of the Domain

CommandLine administration via weblogic.Admin

Deprecated weblogic.Admin, introduced WLST

WebLogic Domain Name in MBean's ObjectName, ex: mydomain:Name=myserver,Type=Server

Changed to com.bea, ex: com.bea:Name=myserver,Type=Server

config.xml represented all WLS configuration

{domain_dir}/config directory represents WLS configuration i.e config is spread across multiple xml files (JMS, JDBC & WLDF config in different files)

None

Service MBeans to get to the root Mbeans

Execute Queues control Thread pool control

Work Manager gives more effective and efficient Thread pool control, like JVM crash can be controlled,

Welogic console combination of Applet and webpage less in synchroniztion, no possibility to extention of console.

New WebLogic console in Portals and easy to extention of the console

No that much integrated

Newly introduced webLogic Diagnostics Framework WLDF is more useful for diagnostics

At a time single version archive is allowed for deployment

Deployment can be done with application version wise from commandline

JMS only two types

JMS new types introduced for more flexibility Store and Forward (SAF), distributed destination

 

Domain Templates are excellent feature for creating multiple domains for a development.

 

Node Manager can start even Admin Server and the commands can be given from WLST


 

 

12. What is Tivoli?why we use?How it works?

Tivoli is a IBM product for profiling tool WebLogic was having similar tool Merqury.

 

13. In order to see last 20 files what is the command?

At your Unix prompt you can give as follows:

ls -lrt | tail -20


14. In order to see last 20 days files what is the command ?

 Simple way is using find command with ctime option and specify days signs +20



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15. If SSL certificates are expired what to do?

Two options:

1. Using temporary demo certificates.

2. Get new renewal from CA(Certifying Authority) like verisign.

 

16. How to select where and which driver we have to use?

This is a typical question. This is obsolutely depends on application context.

Major impacting factors

i) load capacity number of connections

ii) Application contains PreparedStatements, CallableStatements preferable is OCI if it is Oracle. (DB vendor specific driver)

iii) Thin Driver is preferable for certain number of connections only. But is most widely used with Oracle RAC and Grid databases.

 

17. How to monitor the incoming  traffic for webserver?

HP OVO, Patrol, access logs of web servers. By looking in the access logs of the web-server.

 

18. How to find network outages in environment?

Basically ping command will give required output if not outage can be predictable, In WebLogic instance to instance inter-communication breakage will be indicated by BEA-000117 error code.

netstat -na |grep using port can be used for identifying the instance is responding or not.

 

19. How  you will analyse threads state using samurai tool?

By getting the Thread dump for the impacted WebLogic instance. Normally, thread state could be ACTIVE, STANDBY, STUCK, If the state is same for many thread dumps then need to check about that thread. 

Check for the 'wait', 'lock' keywords with find option, verify how the threads impacting, does it leads to dead-lock? It is GUI tool which clearly shows in RED color which are the impacting threads in wait state.

 

20. Basic requirement for datasouce and connection pools?

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The Basic need for Connection Pool and DataSource are:

1. connection to the adminserver

2. JDBC Driver name, connecting parameters such as DataSource name, DATABASE schema details (user,password, hostname, port, SID)

3. Target the connection pool to a 'server' or 'cluster'.

4. Finally verify the connection pool by testing it.


What is the difference between TRUNC and DELETE in SQL commands?

TRUNC

faster

dependent tables cannot work


DELETE

slow

row-by-row

cannot applicable for large tables


http://www.softstuff-consulting.com/kbase/showkb.asp?id=15


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