A process section is defined as "a group of contiguous virtual pages
with the same characteristics, such as writability and shareability"
When you run an image, memory must be segregated into sections to make
sure it is used correctly. For example, CODE is not writeable, nor are
constants. You can see the image sections created by the linker for
a particular program by examining the link map. (see LINK/MAP)
A complex image may require many process sections, but it's not
practical to allow an unlimited number, hence the system wide limit
PROCSECTCNT. The default value (32) is often sufficient, but is perhaps
a bit on the low side (it was high for 1979). 64 is probably a more
reasonable value for todays images.
Note that PROCSECTCNT is not a hard limit. The process section table
data structure can "overflow" into unused parts of the process working
set list - for example, if a process's WSEXTENT is less than WSMAX, the
unused space can be used for extra process section entries. In a pinch
you may be able to get around a SECTBLFUL error without rebooting by
reducing WSEXTENT on the process getting the error.
For all practical purposes, the details are not really important. If
you are consistently getting SECTBLFUL errors, you should probably
raise PROCSECTCNT. I wouldn't worry about going as high as 96. If you
continue to get errors, examine the MAP files to determine why the
image needs so many sections.