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DR_UNIT_BASE is a GEN system parameter that specifies the base value from which unit numbers for DR devices (DIGITAL StorageWorks RAID Array 200 Family logical RAID drives) are counted.

DR_UNIT_BASE provides a way for unique RAID device numbers to be generated. DR devices are numbered starting with the value of DR_UNIT_BASE and then counting from there. For example, setting DR_UNIT_BASE to 10 produces device names such as $1$DRA10, $1$DRA11, and so on.

Setting DR_UNIT_BASE to appropriate, nonoverlapping values on all cluster members that share the same (nonzero) allocation class ensures that no two RAID devices are given the same name.