The total amount of paging space is often determined by trial and error. One commonly used guideline is to double the RAM size and use that figure as a paging space target. The most common problem regarding paging space is caused by running out of allocated space. If paging space runs low, processes can be lost, and if paging space runs out, the system can panic. The following signal and error information can help you monitor and resolve or prevent paging space problems.
The operating system monitors the number of free paging space blocks and detects when a paging-space shortage exists. When the number of free paging-space blocks falls below a threshold known as the paging-space warning level, the system informs all processes (except kprocs) of this condition by sending the SIGDANGER signal. If the shortage continues and falls below a second threshold known as the paging-space kill level, the system sends the SIGKILL signal to processes that are the major users of paging space and that do not have a signal handler for the SIGDANGER signal. (The default action for the SIGDANGER signal is to ignore the signal.) The system continues sending SIGKILL signals until the number of free paging-space blocks is above the paging-space kill level.
Processes that dynamically allocate memory can ensure that sufficient paging space exists by monitoring the paging-space levels with the psdanger subroutine or by using special allocation routines. You can use the disclaim subroutine to prevent processes from ending when the paging-space kill level is reached. To do this, define a signal handler for the SIGDANGER signal and release memory and paging-space resources allocated in their data and stack areas and in shared memory segments.
If you get error messages similar to the following, increase the paging space:
INIT: Paging space is low!
OR
You are close to running out of paging space. You may want to save your documents because this program (and possibly the operating system) could terminate without future warning when the paging space fills up.
To increase the size of your paging space, see Changing or Removing a Paging Space or Resizing or Moving the hd6 Paging Space.