SCF Reference Manual for the Storage Subsystem (G06.28+, H06.05+, J06.03+)

NOTE: To change the primary or backup processor values for a disk, stop all the disk paths
(STOP DISK command) or terminate the disk process (RESET DISK, FORCED). Then you can alter
the disk configuration with new PRIMARYCPU and BACKUPCPU values.
You typically swap processors for a disk when load balancing the system or preparing for disk
replacement.
PRIMARY DISK Consideration
For G06.10 and earlier RVUs, using the PRIMARY command to swap a disk to its backup processor
can affect the other disk processes using the same SACs. See:
• “PRIMARY Command Function in G06.00 Through G06.10” (page 125)
• “PRIMARY Command Function in G05.00 and Earlier” (page 128)
An Example for G06.11 and Later RVUs
On G06.11 and later RVUs, SACs in the same topology branch are owned by both processors.
The PRIMARY command can change which processor actively uses a SAC, but it does not change
SAC ownership.
Because both processors in the same topology branch can use the same SAC, the PRIMARY
command does not create an access problem for the other processor.
In the figures that follow:
• SACs and disks controlled by processor 2 are shaded.
• Active paths, fabrics, and SACs are in bold.
• Backup disk processes are represented with a prime mark: for example, $D0201'.
110 Managing Disks