Method and means for execution of commands accessing variable length records stored on fixed block formatted DASDS of an N+2 DASD synchronous array

Variable length records can be accessed from an array of N+2 synchronous fixed block formatted DASDs in a single pass and in the presence of a single DASD failure if each record is partitioned into a variable number of K fixed length blocks, the blocks are written on the DASDs in column major order K modulo (N+1), the order is constrained such that the first block of each record resides on the (N+l)st DASD, a parity block for each column resides on an (N+2)nd DASD, and each parity block spans N blocks in the same column from the first N DASDs and one block one column offset thereto on the (N+1)st DASD.