I read it on the following forum
which basically has the following post
Basically you are doing too much output before you decide to you need to forward to a new page.
Output could just be the plain HTML text in the jsp document - that all gets converted to out.println();
Basically if it writes more than your buffer (default is 8kb) then the buffer is flushed, and you can't forward/redirect anymore as you are committed to complete the current response.
There are two ways of handling this issue
1 - shift your forward/redirect code, so that it happens as early as possible. BEFORE any HTML is output.
2 - increase the buffer size. <%@ page buffer="16kb"%> for instance.
This means it can write out more text before you decide to forward.
That might stop the error on your page.
3 - Oh, and if you have set your buffer to zero, or you have directly called flush() somewhere in your code, that would be the cause. Don't do those things :-)
Can someone tell me does it have a performance impact if we increase or decrease page buffer