Browse Prior Art Database

Sync Field Verification of Disk Records

IP.com Disclosure Number: IPCOM000041731D
Original Publication Date: 1984-Mar-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Danen, JA: AUTHOR [+2]

Abstract

A sync field is written prior to each ID or data record on a hard file to allow the data channel circuits to be synchronized to the data on the disk during a read operation. The sync field ends in a sync byte which identifies the end of the sync field and the start of the ID or data record. Previously, the sync field and sync byte were not verified to be written with the correct patterns. This technique examines key bits in the data stream from the attachment during the beginning of each write operation. Each time one of these bits is detected, the last byte of data received is analyzed to determine if it was a valid pattern. If only valid patterns have been detected prior to the time a sync byte pattern is found, the sync field is accepted as good.

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Sync Field Verification of Disk Records

A sync field is written prior to each ID or data record on a hard file to allow the data channel circuits to be synchronized to the data on the disk during a read operation. The sync field ends in a sync byte which identifies the end of the sync field and the start of the ID or data record. Previously, the sync field and sync byte were not verified to be written with the correct patterns. This technique examines key bits in the data stream from the attachment during the beginning of each write operation. Each time one of these bits is detected, the last byte of data received is analyzed to determine if it was a valid pattern. If only valid patterns have been detected prior to the time a sync byte pattern is found, the sync field is accepted as good. A 'data unsafe' error will be posted to the system if an invalid pattern was detected at any time prior to the time a sync byte was detected or a sync byte was not detected during a write operation. This check is important because noise on the interface to a file could cause extra bits or missing bits in the data from the attachment. These extra or missing bits will be corrected in the data field of a file using an error correcting code but could cause a sync byte to be unrecognizable. If the sync byte cannot be found, the entire ID or data record is unreadable. A portion of the sync field prior to the sync byte must also be properly written to ensure detection of the sync byte;...