Patent ID: 6098148
Filing Date: 2000-08-01
Classification: G06F

Abstract:
In a direct access storage device (DASD), said DASD containing a sequence of machine-readable digital data including:multiple record groups, each record group including multiple data records each preceded by a record header, each data record and each record header having a beginning address in the data storage medium, wherein at least one of the record groups includes a marker code; anda volume trailer concluding said sequence, said volume trailer including, for each record group:a pointer field containing the beginning address for the record group;a group count field containing a count of data records for the record group; anda marker count field containing a count of marker codes for the record group;a computer implemented method of advancing from an original address to a target address containing the next marker code following the original address, said method comprising:consulting the volume trailer to determine a number of marker codes in an original record group;if the original record group contains marker codes, sequentially advancing through each remaining record until reaching a first one of the following: a first marker code, or an end of the original record group;if the end of the original record group is reached, or if the original record group does not contain any marker codes, consulting the volume trailer to determine whether any record groups subsequent to the original record group contain any marker codes,if no record groups subsequent to the original record group contain any marker codes, issuing an error message;otherwise, if one or more record groups subsequent to the original record group contains any marker codes,consulting the volume trailer to identify a beginning address for a first one of said record groups subsequent to the original record group containing any marker codes, andsequentially reading each record header in the first record group starting at the beginning address until reaching the first marker code in the first record group.