For Sun Solaris, you can set both soft and hard limits for file descriptors. The soft limit can be increased up to the hard limit by the user, but the hard limit can be increased only by someone with “root” permissions. The soft limit determines the number of open file descriptors available to an Adaptive Server engine.
Although most of the open file descriptors are available for user connections, a few are used by Adaptive Server engines for opening files and devices.
See the System Administration Guide for additional information on user connections.