Browse Prior Art Database

Sequential Search Technique

IP.com Disclosure Number: IPCOM000080233D
Original Publication Date: 1973-Nov-01
Included in the Prior Art Database: 2005-Feb-27
Document File: 3 page(s) / 68K

Publishing Venue

IBM

Related People

Harboe, RW: AUTHOR [+2]

Abstract

The following technique is used to improve the search speed with respect to a disk file, wherein records are arranged in ascending order on a series of parallel tracks or cylinders, each oi which is partitioned into a plurality of data sectors. Upon initiation of the command to search the sequential content, the record at the current disk address (CDA) is read into the current buffer and compared to a mask. The search will terminate with an error, if the record entered is high compared to the mask and the current disk address equals the start of extent sector (S0ES or the location of the first data record). An error condition will also occur if the record is low compared to the mask and the current address equals the end of the data sector minus 1 (EODS minus 1).

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Sequential Search Technique

The following technique is used to improve the search speed with respect to a disk file, wherein records are arranged in ascending order on a series of parallel tracks or cylinders, each oi which is partitioned into a plurality of data sectors. Upon initiation of the command to search the sequential content, the record at the current disk address (CDA) is read into the current buffer and compared to a mask. The search will terminate with an error, if the record entered is high compared to the mask and the current disk address equals the start of extent sector (S0ES or the location of the first data record). An error condition will also occur if the record is low compared to the mask and the current address equals the end of the data sector minus 1 (EODS minus 1).

If the search was initiated at the first sector of the file and the record was low or deleted, the last record on the initial cylinder of the file is read and compared against the mask. If this record is also low or deleted and the current address is no closer than three cylinders from the end of the file, the last record of the every third cylinder will be read until the record is high compared to the mask, or until the current address is less than three cylinders from the end of the file. If the current address is closer than three cylinders to the end of the file, then the current address is incremented to read the last record in the file.

During the process a counter is used to keep track of how many cylinders have been skipped. The counter is incremented by three if the records were deleted. 0therwise, it is reset to zero and incremented by two, while the address of the first record on the cylinder subsequent to the current disk address is saved. If the record in the last sector of the file was high or deleted, the current disk address is decremented to read the first record on the last cylinder of the file.

If this record was low compared to the mask, the last data cylinder of the file will be scanned for a match. If the record was high, the current disk address is decremented o...