After encounter some problem at work running large Oracle databases on a
RHEL4 system, we need to prevent kernel overcommit from exceeding a
certain threshold. In fact, the problem was that the system begin to
kill processes under heavy load: in our case ssh connections...
Ouch!
The solution was to alter the default behavior of the Linux kernel in
this area, as mentioned in Documentation/vm/overcommit-accounting in
the corresponding source code tarball.
Interestingly, an overall and great explanation of this mechanism is available today on the O'Reilly LinuxDevCenter.com. It is worth reading it, i think.