How come there are zombie processes?

[Zhang Zhao gui]

I noticed that there are about six zombie or defunct processes in the system,
will they still consume system resources? How can I clean them up? Why am I
getting this kinds of processes? Will it affect the system performance? Are
there any guidlines on how to solve such a problem? Is there any limit on the
maximum number of zombie processes?
Thanks in advance for your advices

[Dan Hull]

Zombies can be created in a variety of ways. One common way is when a process'
parent dies, its parent ID reverts to 1 (the system). If the process itself
then dies, it becomes a zombie, since its parent isn't there and it's not
reaped.

The only way to get rid of a zombie that won't die from a kill -9 is to reboot
the system. Normally they shouldn't eat many (if any) resources.

[Dave Matthews_1]

Get Doc ID WP1030010A. This document explains that zombies are a normal
occurance. The document explains that once a process ends it leaves behind a
zombie as a record of its execution for the parent process that spawned it.