Seeing the error /proc/sys/vm/nr_pdflush_threads: Operation not permitted when attempting to set vm.nr_pdflush_threads on Red Hat Enterprise Linux 4 & 5 kernels.

Issue

• User attempts to change the number of pdflush threads using sysctl or echo (sysctl -w vm.nr_pdflush_threads=4 or echo 4 >  /proc/sys/vm/nr_pdflush_threads)
• Error appears on console.
• vm.nr_pdflush_threads remains unchanged.