Emulation technique for variable-length disk system to access data in a fixed-length disk system

摘要

A disk system which, when a variable-length disk is emulated using a fixed-length disk, makes it unnecessary to perform extra disk accesses at the time of performing a reading/writing operation the fixed-length disk. The disk system includes an upper system that accesses data with the use of a variable-length formatted form, a disk control unit emulating the variable-length disk and performing control of the fixed-length disk, and a fixed-length formatted disk unit. A storing region in the disk unit is separated into two regions. Count areas in all CKD records are stored into one of the regions, and key areas and data areas in all the CKD records are stored into the other region. The count areas in all the CKD records, which have been stored in the one of the storing regions, are stored into a cache memory in the disk control unit. When an access is executed from the upper system to the disk unit, the count areas stored in the cache memory are referred to so as to search an object record. This allows an access to the disk unit to be executed only to the objective record thus searched.