In an online, real-time system, which of the following would be most likely to be used as backup for an application's master file maintained on magnetic disk?
A) At specified periods the disk files would be dumped to (copied on) magnetic tape along with the period's transactions
B) A duplicate disk file would be maintained and all activity would be copied on magnetic tape continuously
C) The grandfather-parent-child technique would be employed to retain disk files
D) All source documents for transactions would be retained
E) The disk files would be copied to magnetic tape continuously
You did not list the choices
at specific periods, the disk files are dumped
a duplicate disk file would be
maintained
To determine which option would be most likely to be used as backup for an application's master file maintained on magnetic disk in an online, real-time system, let's evaluate each option and consider their effectiveness in terms of backup and recovery:
A) "At specified periods the disk files would be dumped to (copied on) magnetic tape along with the period's transactions." This option suggests periodic backups of the disk files to magnetic tape, along with the corresponding transaction data. It would provide a backup point that includes all the transactions up to that point. This method is commonly known as incremental backup and is a popular backup strategy.
B) "A duplicate disk file would be maintained, and all activity would be copied on magnetic tape continuously." This option suggests having a duplicate (or mirror) disk file that is continuously updated with all the activities occurring on the primary disk. Additionally, a continuous backup to magnetic tape is performed. This method is known as synchronous mirroring and would provide real-time backup and recovery capabilities.
C) "The grandfather-parent-child technique would be employed to retain disk files." The grandfather-parent-child technique, also known as a rotating backup scheme, involves maintaining multiple copies or versions of the disk files. Typically, this includes daily, weekly, and monthly backups with retention periods. This method allows for point-in-time recovery at different intervals.
D) "All source documents for transactions would be retained." This option suggests retaining all the source documents for the transactions rather than focusing on the backup of the master file itself. While this could be useful for auditing purposes or transaction-level recovery, it does not address the backup of the master file directly.
E) "The disk files would be copied to magnetic tape continuously." This option is similar to option B, suggesting continuous backup of the disk files to magnetic tape. It provides real-time backup capabilities similar to synchronous mirroring.
Considering the given options, options B and E both suggest continuous backup of the disk files, which would be suitable for an online, real-time system. These options ensure that any updates or changes to the master file are immediately backed up and can be recovered in case of a failure.
Therefore, the most likely choice for backup in an online, real-time system would be either option B or E, where a duplicate disk file is maintained and all activity is continuously copied to magnetic tape.