Method for utilizing a longitudinal track on a helical scan tape data storage system to provide a fast search capability

• US 5,566,032 A
• Filed: 07/20/1995
• Issued: 10/15/1996
• Est. Priority Date: 11/12/1991
• Status: Expired due to Term

• Current Assignee: Storage Technologies Corporation (Oracle Corporation)
• Original Assignee: Storage Technologies Corporation (Oracle Corporation)
• Inventors: Cleveland, Brian G., Hansen, Douglas C., Dodt, William C.
• Primary Examiner(s): Psitos, Aristotelis
• Assistant Examiner(s): WILSON, JAMES
• Application Number:
  US08/504,540
• Time in Patent Office: 453 Days
• Field of Search: 360/72.2, 360/78.07, 360/14.2, 360/72.1, 360/72.3
• US Class Current: 360/72.2
• CPC Class Codes: G11B 15/087 by sensing recorded signals
• CPC Class Codes: G11B 15/1816 Programmed access in sequence to indexed parts of operating tapes cooperating with rotating heads see provisional also G11B15/005
• CPC Class Codes: G11B 15/1875 adaptations for special effects or editing signal processing or indexing therefor G11B27/00
• CPC Class Codes: G11B 15/20 Moving record carrier backwards or forwards by finite amounts, i.e. backspacing, forward spacing
• CPC Class Codes: G11B 20/1207 with transverse tracks only
• CPC Class Codes: G11B 2220/90 Tape-like record carriers
• CPC Class Codes: G11B 27/107 of operating tapes
• CPC Class Codes: G11B 27/3027 used signal is digitally coded
• CPC Class Codes: G11B 27/32 on separate auxiliary tracks of the same or an auxiliary record carrier
• CPC Class Codes: G11B 27/323 Time code signal, e.g. on a cue track as SMPTE- or EBU-time code
• CPC Class Codes: G11B 27/328 on a tape [TTOC]

Abstract

A novel method is disclosed for performing a high speed search for a selected data block or data file utilizing any one of several presently existing helical scan tape formats which utilize, in addition to the helically scanned tracks, one or more longitudinal tracks for recording indexing information indicative of the location of data blocks and file marks stored on the associated helical tracks. Data file location information is written to a header area on a series of helical tracks and to one (or more) of the longitudinal tracks when a data block or a file mark is written to a tape. A high speed search for a desired data block or data file can then be performed using this track location information.

Claims

1. In a data recording system using magnetic tape for storing data, said recording system connected to a host computer, said recording system using a recording format on said magnetic tape employing a plurality of helically scanned tracks for storing said data, including a first longitudinal track for storing magnetic tape position information indicative of location of said data and a second longitudinal track containing position marks and servo control pulses, said position information being written at equally spaced predetermined locations on a said first longitudinal track, said position information comprising a plurality of file marks and sector marks said data being logically segmented into files containing sectors comprising data blocks, and wherein said data recording system uses a tape drive control unit to store a memory copy of said header area from said magnetic tape, a method for locating a selected block in response to a command from said host computer, said command including indicia of location of said selected data block comprising the steps of:

placing a header area on said helically scanned tracks for locating said selected block, said header area containing indicia of location of said data blocks comprising the number of said servo control pulses between said header area and a location of each of said blocks;

reading said memory copy of said header area to determine whether valid magnetic tape position information is contained therein; and

employing redundant strategies for locating said selected data block, one of said strategies being selected according to a data integrity of said header area, said strategies further comprising the steps of;

using, in response to a situation wherein said header area is useable by said recording system, said indicia of location in said header are to locate said selected data block by counting said servo control pulses on said second longitudinal track;

using, in response to the situation wherein said header area is unusable by said recording system, data stored on said servo control track to first locate said sector mark delineating the sector preceding the sector containing said selected data block by counting said servo control pulses on said second longitudinal track prior to location closed selected data block; and

using, in response to a situation wherein said header area is useable by said recording system, and wherein said indicia of location of said data blocks is not consistent with said indicia of location in said command from said host computer, data stored on said second longitudinal track to first locate one of said position marks delineating the file containing said selected data block prior to locating said selected data block.

2. The method according to claim 1 wherein said data stored on said first longitudinal track include scan group frames.

3. The method according to claim 1 wherein said position marks are sub-sector marks.

4. The method according to claim 1 wherein locating said selected data block alternatively includes locating a scan group for said selected data block on said first longitudinal track.