PURPOSE: To minimize the time of access to a variable-length record which is defined in an array of N+2 synchronous type fixed-block formatted DASDs. CONSTITUTION: The variable-length record is accessed through a single path from the array of N+2 synchronous type fixed-block formatted DASDs. If a fault occurs to one DASD and each record is sectioned into fixed-length blocks as may as a variable K, the blocks are written in the DASDs in column preferential order K based upon (N+1) as a rule. The column preferential order is so limited that a 1st block of each record is an (N+1)th DASD. A parity block of each column is an (N+2)th DASD. Respective parity blocks span N blocks in the same column from 1st N DASDs and one block one column on the (N+1)th DASD which is offset to it.
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