Patent ID: 7082496

Claim:
A disk storage system comprising: a disk storage unit having a plurality of records capable of being accessed by a data processing unit, each of said records having a variable length data field for storing data and a control field which includes data indicating a length of the data field; and a control unit connectable to said data processing unit, having a controller and a cache memory for storing data of some of said plurality of records of said storage unit; wherein said controller receives a write request and write data from said data processing unit to update data stored in said variable length data field of one said record except data stored in said control field, regardless of whether or not said one record is stored in said cache memory, and if said write data received from said data processing unit does not meet a condition with respect to the variable length data field of said one record, said controller notifies said data processing unit of an error message without accessing said one record of said storage unit.