concurrency issue

Hi all,
I have a problem in struts say, If two different users submits their data at same time am getting null pointer exception HTTP status 500 error. In log file it doesn't states any error. What are all the various possible reasons of getting like this can any one suggest me an idea to sort out it out.

Note: If only one user submits the data at a time there is no error. It perfectly takes to next page

Which version of struts you are using .. struts2 or struts1.x?

am using struts 1.3

Where do you see the NullPointerException ? written to the browser ? Exception trace is not available?
try chaning the bean scope to "request" and see ..

Say its a user registration form each person fills data and submit if they submit individually no error it gets insert. but if they submit at a time it shows error in browser as 500 error null pointer exception. In error log nothing error has described

Sounds it is programmatic issue and the way you are handling the shared objects in the Action classes/Beans .This Issue does not seems to be originated from the framework, try putting more logs/debugs ..
Good luck.

rerards.

Thank you manjesh let me see to it