The system configuration file customizes various parameters in the kernel. This file is read-only at boot time, so changes require a reboot to take effect. The following are example configuration lines.
set autoup=600 set nfs:nfs4_nra=16
This first line sets the parameter autoup to be 600. autoup is a fsflush parameter that defines the age in seconds at which dirty pages are written to disk. The second line sets the nfs4_nra variable from the nfs module to be 16, which is the NFSv4 read-ahead block parameter.
A common reason that /etc/system was modified was to tune kernel parameters such as the maximum shared memory, the number of semaphores, and the number of pts devices. In recent versions of Solaris, some of these commonly tuned parameters have been made dynamic or dynamically changeable, as described in prctl Command on page 446 of Solaris Performance and Tools. You must still edit /etc/system for less commonly used parameters.