Abstract: A partitionable computing system includes main storage units on respective sides of the complex which can be fully controlled and accessible from either side. The system includes a dual port main storage unit design, and a system controller design capable of driving plural main storage unit interfaces. With this configuration, one system controller and the processors attached to that system controller can be taken offline and partitioned off to perform maintenance while all of the physical main storage units remain accessible to the processors on the surviving side of the complex. The operating system sees no loss available memory and the time to perform the maintenance activity is significantly reduced.