| 摘要 |
In a method and means for accessing arrays of DASDs, write update of variable length records stored in row major order on an array of N DASDs is facilitated by utilising the correlation between byte offsets of a variable length record and the byte offset of a byte level parity image of data stored on the same track across N-1 other DASDs. Each DASD physical track has a home address field HA, a record zero field RO, one or more count fields C and one or more data fields D. Each count field C is followed by a variable length block data field D. Parity is recorded in the data field in physical track N in the DASD N. If data field D3 is to be updated and is five bytes long, the old and new values of D3 are XORed and the old value of the last five bytes in D8 is changed to match this. <IMAGE> |
