Patent ID: 6691115
Filing Date: 2004-02-10
Classification: G06F,Y10S

Abstract:
A method of operating a backup system so as to replicate database updates performed on a primary system, the method comprising:receiving a first stream of first audit records from the primary system, the first audit records including first audit update records indicating database updates generated by transactions executing on the primary system and control point records defining control time frames at which the first audit update records were generated by the primary system; upon receiving each of the control point records, generating a system transaction record representing a range of transaction identifiers for transactions executed in the primary system during the control time frame associated with the control point record, the system transaction record further having a control point count representative of the control time frame; storing the first audit update records in one or more first image trails, and storing each first image trail in first image trail files; storing in each first image trail file a control point count for identifying the control time frame at which the first image trail file is created; concurrently for each of the first image trails, applying the first audit records to a backup database in the sequence of the first image trail files; and periodically executing a file purge procedure for purging image trail files no longer needed, including: building a composite system transaction record to identify a maximum span of transaction identifiers corresponding to control time frames associated with the first audit records currently applied to the backup database, selecting one of the first image trail files and identifying the control point count stored in the selected first image trail file; retrieving a first one of the system transaction records that corresponds to the identified control point count; and comparing a first set of transaction identifiers in the first system transaction record to second set of transaction identifiers in the composite system transaction record, and purging the accessed first image trail file provided all of the transaction identifiers in the first set are older than corresponding transaction identifiers in the second set.