SCSI-3 is required for configuring Active/Active (A/A) load balancing in a clustered environment. SCSI-3 is enabled by default when DMP is installed in a clustered environment.
If the disk resources have already been created before setting SCSI-3 support at array level, then they are reserved using SCSI-2 and A/A load balancing policies will not work on those disks.
To use A/A load balancing, enable SCSI-3 reservation for all disk under an array using the vxdmpadm setarray command. This ensures that the disks under the selected array will be reserved using SCSI-3 even if the cluster application issues SCSI-2 reservation for these disks.
Syntax for vxdmpadm setarray command:
vxdmpadm setarrayscsi3 scsi3support=1 Harddisk name.
Refer to the Dynamic Multi-Pathing Administrator's Guide for details.