WebLogic Interview questions and answers
1)What is web.xml?
Web.xml is an XML document that is mainly for application purpose and it helps in listing out the J2EE components and configuration that of your application in J2EE modules format.
2)What are the capabilities of WebLogic server?
There are various capabilities associated with WebLogic server and they are
... Changes in dynamic configuration.
... Production application redeployment.
... Rolling upgrades.
3) Explain about the function associated with T3 in WebLogic server?
T3 provides enhancements support for the messages of WebLogic server. The enhancements comprise of the object replacement, the working of the weblogic server - clusters and also HTTP. T3 also performs serialization of java object and also predation of RMI. T3 can be considered as superset associated with JAVA object. T3 is mandated between WebLogic servers, programmatic clients and cluster associated with WebLogic server. The protocols HTTP and IIOP are made used for enabling communication between WebLogic server and processes.
4) Explain the use of HTTP?
HTTP is the protocol that is made used for the purpose of enabling communication between the WebLogic server and processes.
5) Explain the functionality of IIOP?
IIOP is a kind of protocol helpful in enabling the communication between WebLogic server and object request broker.
6) How do you differentiate between a server hang and server crash issue?
When a server crashes, the JAVA process no longer exists.
When Server is hang, it stops responding.
We can use the weblogic.ADMIN utility to ping the server. In case of hang situation we can take multiple thread dumps and analyse the cause of hang.
7) What can be the various reasons for a server crash?
... Native IO
... JVM
... SSL Native Libraries
... Supported Configuration
... JDBC Driver issue
8) Server crash ---- troubleshoot?
JVM crash generates a hs_err_pid file. We need to look into the stack trace of the hs_err_pid file.
Thread is from a native io, we need to disable native io.
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 optimised code, we can turn of optimization.
stack is from native calls of application, its a bug with the application and it has to be modified.
9) Server hang ---- troubleshoot?
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 Ctrl+Break on Windows
Analyze the thread dump to find the root cause.
10) Reasons of Server hang?
.... Memory leak
.... database query taking a longtime to return
.... Deadlock
11) What is memory leak?
Memory leak is when objects are not removed from the heap even when they are not required.
12) What are the variour causes of OUT OF MEMORY?
... Insufficient heap size
... Objects licking too long
... Memory leak in application code.
... Full Garbage Collection (GC) not happening due to JVM Bug.
13) How to 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.
14) When the High CPU Usage occur?
It occurs when one process or one thread utilizes unexpectedly high proportion of CPU.
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