Shared Memory Regions on Darwin
Shared memory regions are set during the system's startup. Unfortunately, once the shared memory regions have been configured on Mac OS X, it appears they can't be changed. Here's how to increase them on your system.
Edit /etc/sysctl.conf (create it if it doesn't exist) and set higher numbers there:
kern.sysv.shmmax=16777216 kern.sysv.shmmin=1 kern.sysv.shmmni=64 kern.sysv.shmseg=8 kern.sysv.shmall=32768
These settings are contained within /etc/rc in 10.3.9 and 10.4.x.
Remember to set all of the 5 values above, otherwise your settings will be overriden by /etc/rc.