HP Process Resource Manager User's Guide

Configuring and enabling PRM on the command line
Configuring PRM
Chapter 7 103
you assign shares to a volume group/disk group for one FSS PRM
group, you must assign shares for that volume group/disk group to
all FSS PRM groups.
• The minimum CPU and memory shares are one. (Assigning one
share is rarely a good idea for any resource.) The minimum number
of disk bandwidth shares you can assign is zero.
• FSS PRM group PRMID numbers must be in a range from 0 to 63 or
from 0 to 255 starting with HP-UX 11i v2 Update 2. (PRMIDs for
PSET PRM groups are assigned by PRM). PRMID 0 is reserved for
the system group, PRM_SYS. PRMID 1 is reserved for the user default
group, OTHERS. PRMID numbers must be uniquely assigned.
• PRM internally creates the group PRM_SYS (PRMID 0) and assigns
system processes to it. Therefore, you do not need to specify a
PRM_SYS group in the PRM configuration file. If you are upgrading an
existing configuration file that contains a PRM_SYS group, delete this
group.
• The PRMID 1 (default name OTHERS) group must appear in the PRM
configuration file. However, you do not need to assign any users to it.
• Users not listed in the configuration file will use the user default
group, PRMID 1 (OTHERS), as their initial group. If your
implementation expects the user default group to carry a significant
load of users, the user default group should have an appropriate
number of shares to meet their needs.
• Root users can occupy any group.
• The configuration file must contain a group/CPU record for each
PRM group you want to create on your system and for all PRM
groups listed in PRM user and application records.
• Do not set memory/CPU and disk shares at opposite ends of the
spectrum and expect to see the desired percentages achieved. If a
process cannot run, it cannot request I/O. Typically, disk shares that
represent over 90% or under 10% of the disk resource will tend to be
less accurate due to such scheduling-induced or demand-induced
fluctuations.
• Several NFS system processes run on behalf of network-generated
requests. If these processes consume substantial CPU, memory, and
disk bandwidth resources from the system group (PRM_SYS), consider
using the prmmove command to move these processes to their own
PRM groups to free up the system group.