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 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.

•Several NFS system processes run on behalf of network-generated requests. If these processes consume substantial CPU and memory 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.

•The internet services daemon, inetd, should be placed in a group other than the system group if the services or their children are using too much CPU or memory resources.

•The user processes of some alternate login methods are not placed in their appropriate initial PRM groups unless PRM’s application manager is running. See “Special case of interest: Client/server connections” (page 99) for more information.

•Pattern matching of alternate names in application records should not generate redundant or conflicting names.

Specifying PRM groups/controlling CPU resource use

You can change PRM groups and their CPU resource use as discussed in the following sections:

•“Adding/modifying PRM groups and CPU allocations ” (page 57)

•“Capping CPU resource use” (page 58)

•“Removing groups/CPU allocations” (page 58)

Reserved PRM groups

When defining your PRM groups, keep in mind that there are two groups reserved by PRM. The reserved PRM group IDs (PRMIDs) are 0 and 1. The group designated by PRMID 0 is the PRM_SYS group, or system group. This group is created automatically and serves as the PRM group for system processes. When a PRM configuration is loaded, existing root logins stay in the PRM_SYS group—unless they have a user record assigning them to other groups. Similarly, new root logins are placed in PRM_SYS, unless a user record indicates otherwise.

By default, PRM gives PRM_SYS 100 CPU shares. If you assign 100 shares to the PRM groups you create, PRM_SYS gets 50% (100/200) of the CPU resource. The PRM_SYS group must get at least 20% of the CPU resource. Thus, if you assign more than 400 shares to your groups, the total shares assigned is greater than 500, and the PRM_SYS group’s 100 shares do not represent at least 20%. In this case, PRM scales the shares for your groups proportionately so they are less than or equal to 400 shares.

54 Configuring and enabling PRM on the command line