weblogic uses the single thread pool for executing the system administrator or application activities. Weblogic receives the executes the requests based on the maximum queue length defined for the thread pool. In case of exceeding this limit, weblogic starts rejecting the web application requests.
We can avoid this by increasing the maximum queue length for the thread pool by making change in Environments > Servers > Threads -> Select an execute thread.
The default value for thread pool is 65536.
Reducing the HTTP Sessions
We can limit the number of HTTP sessions based on the memory allocation which avoids in resulting out of memory errors. The following entry can be done in deployment descriptor file for handling count for HTTP sessions.
Exit from server on Out of Memory exception
performing the exit when out of memory exception occurs provides the automatic shutdown and configure the node manager or high availability tool to restart the weblogic server which reduces the down time for the server.
Add the below entry in the config.xml for automatic shutdown of server