21.Define memory leak ?

Memory leak is the condition that arises when the objects get retained in the heap even after they have no use.

22.What causes the condition OUT OF MEMORY?

There are various reasons that can lead to this condition and they are

• Insufficient size of the heap compared to the extra load.
• Placing of the objects takes longer period of time like that of HTTP sessions.
• Occurrence of memory leak inside the application code.
• The prevention of occurrence of full GC because of JVM bug.

23.How can the OUT OF MEMORY be solved?

There is a possibility for collecting the memory data after enabling GC – verbose. If the condition has aroused because of HTTP session, then it will be automatically solved when the session gets time out. You should also verify the code associated with the handling of jdbc connectivity. You should also optimize the size of the heap by considering the load.

24.When can high usage of CPU occur?

This is the condition that usually occurs when a single thread or process makes use of a larger portion of the CPU in an unexpected manner.

25.How can the issue associated with high CPU usage be solved?

In windows platform the issue of CPU high usage can easily be solved by making use of pslist and also with the process explorer to observe the function performed by the thread or the process.

26.Explain the term clustering?

Clustering is the process of grouping the servers together for accomplishing high percentage of scalability and availability.

27.What is the purpose of clustering?

The major goal of performing the process of clustering is to make high scalability as well as availability of the servers possible. This process also helps in balancing the load in a proper manner and also accomplishes failover.

28.How can cluster communication occur?

The communication through cluster is made possible by the multicast IP as well as port by the process of sending periodic messages which are normally called as heartbeat messages.

29.What are the various types of WebLogic installations?

The WebLogic installation usually occurs in three different modes which are:

• Graphical mode
• Console mode
• Silent mode.

30.What is Graphic mode?

It is a kind of installation type that makes use of interactive GUI.

31.What is console mode?

This is a kind of installation type that follows interactive text based method.

32.What is silent mode?

This is a method of installation that is non-interactive and is usually based on the .xml properties – file.

33.What is Unicast?

Unicast is the method used in the clustering technique where there are cluster master and each server should ping to this cluster master for informing that the server is alive.

34.What is Multicast?

It is a kind of clustering system where there is no cluster master and each and every server needs to ping each other for informing their existence. Multicasting has many messages to be sent in the form of ping as each server needs to inform all others about its existence. This condition creates much complexity associated with the method compared to unicast.

35.What is a stage deployment?

Stage deployment is a kind of process in which the admin gets a physical copy which is distributed to the other instances.

36.What is non-stage deployment?

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.

37.How can port number be checked?

Port number can be checked by using netstat-na|grep connected.

38.How to find out the listening ports?

Listening ports can be found out by using netstat-na|grep listen.

39.How to check the version of Java?

Version of java can be checked by using [roo@h1vm/]#java-version.

40.How is it informed when the server is added to the cluster?

The availability of the new server in the cluster is broadcasted by the WebLogic server – cluster.