Sun Java System Web Server can support both kernel-level and user-level threads whenever the operating system supports kernel-level threads. Local threads are scheduled by NSPR (Netscape Portable Runtime) within the process, whereas kernel threads are scheduled by the host operating system. Usually, the standard debugger and compiler are intended for use with kernel-level threads. By setting KernelThreads to 1 (on), you ensure that the server uses only kernel-level threads, not user-level threads. By setting KernelThreads to 0 (off), you ensure that the server uses only user-level threads, which may improve performance.
The default is 0 (off).