ITPEC FE Morning April 2023 Question 19
Among the different types of backup methods, which of the following is incremental backup? Here, in the first backup, all files are backed up and the information that indicates a file update managed by the operating system is reset.
Explanation
Only updated files are backed up, and the update flag is reset — an incremental backup copies what changed since the previous backup of any kind.
The operating system sets an update flag (the archive bit) on a file whenever it changes. Backup types differ in which files they copy and whether they clear that flag:
Because an incremental backup resets the flag, the next one copies only what changed after it, and a restore needs the full backup plus every incremental backup in order. A differential backup leaves the flag set, so each one copies everything changed since the last full backup, and a restore needs only the full backup and the latest differential.
Answer (d)
Why not others:
- •(a) — copies all files but leaves the flags set: a full copy that does not mark files as backed up (a copy backup)
- •(b) — the full backup described in the question: all files, flags reset
- •(c) — the differential backup: updated files only, flags left set, so changes accumulate until the next full backup
Key rule: Differential and incremental backups both copy only changed files; whether the flag is reset decides if each backup grows from the last full backup or restarts from the last backup.
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