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.