SY0-501 · Question #23
A database backup schedule consists of weekly full backups performed on Saturday at 12:00 A.m. and daily differential backups also performed at 12:00 A.m. If the database is restored on Tuesday…
The correct answer is B. 2. To restore a database using a full and differential backup strategy, the recovery process requires applying the most recent full backup followed by the latest differential backup taken after that full backup but prior to the desired restore point.
Question
A database backup schedule consists of weekly full backups performed on Saturday at 12:00 A.m. and daily differential backups also performed at 12:00 A.m. If the database is restored on Tuesday afternoon, which of the following is the number of individual backups that would need to be applied to complete the database recovery?
Options
- A1
- B2
- C3
- D4
How the community answered
(17 responses)- B82% (14)
- C12% (2)
- D6% (1)
Why each option
To restore a database using a full and differential backup strategy, the recovery process requires applying the most recent full backup followed by the latest differential backup taken after that full backup but prior to the desired restore point.
One backup would only be sufficient if the restore point was immediately after a full backup and no differential backups were taken, or if only a full backup was available and acceptable for recovery, which is not the case here.
The recovery requires applying the full backup from Saturday 12:00 A.m. as the base. Subsequently, the differential backup from Tuesday 12:00 A.m. must be applied, as it contains all changes since the last full backup (Saturday) up to Tuesday 12:00 A.m., providing the most recent state before the Tuesday afternoon restore point. This totals two backups.
Three backups would be unnecessary in this scenario, as a differential backup cumulatively captures all changes since the last full backup, meaning only one differential is needed to bring the full backup up to date.
Four backups is excessive for a recovery involving a single full and a single differential backup, indicating a misunderstanding of how differential backups are applied in a recovery sequence.
Concept tested: Database restore using full and differential backups
Source: https://learn.microsoft.com/en-us/sql/relational-databases/backup-restore/differential-backups-sql-server
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