If your Digital UNIX system is freezing up with system error messages
of "vmunix: fork/procdup: thread_create failed", then likely
you do not have the system kernel parameter max-threads-per-user set to
a high enough value for the number of threads executing in processes
running under the pmdf account.
The current values of your system kernel parameters may be viewed via the command:
# sysconfigdb -lor
# sysconfig -q proc
If the current values are not high enough for the sort of PMDF load you expect, you should increase the values using the sysconfigdb utility and then reboot your system so that the increases take effect.