WEBLOGIC Frequently Asked Questions faq

Memory leak is when objects are not romved from the heap even when they are not required.

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.

Trail & Error

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.

Stuck threads are JVM threads that have been running for more than a certain configurable time (default 600 seconds)

Garbage collection is the JVM’s process of freeing up unused Java objects in the Java heap.The Java heap is where the objects of a Java program live. It is a repository for live objects, dead objects, and free memory. When an object can no longer be reached from any pointer in the running program, it is considered “garbage” and ready for collection.

The JVM heap size determines how often and how long the VM spends collecting garbage. An acceptable rate for garbage collection is application-specific and should be adjusted after analyzing the actual time and frequency of garbage collections. 

A domain is the basic administration unit for WebLogic Server. It consists of one or more WebLogic Server instances, and logically related resources and services that are managed, collectively, as one unit.

Administration Server  A domain always includes one WebLogic Server instance that is configured as an Administration Server. The Administration Server provides a central point for managing the domain and providing access to the WebLogic Server administration tools. These tools include, but are not limited to, the following:

WebLogic Server Administration Console—graphical user interface to the Administration Server

WebLogic Server Node Manager—Java program enabling you to start, shut down, restart, and monitor remote WebLogic Server instances

Managed Servers  All other WebLogic Server instances in a domain are called Managed Servers. Managed Servers host application components and resources, which are also deployed and managed as part of the domain. In a domain with only a single WebLogic Server instance, that one server functions as both the Administration Server and Managed Server.