Differential Backup Timing

Perform differential backups as a supplement to full backups. Because they are usually faster and smaller, you can perform them more often than full database backups. They are also typically more efficient because they require less space on media and have a briefer impact on database performance than frequent full backups. Additionally, you can use them to minimize the number of Transaction logs you need to recover during a restore, because you need to restore only the Transaction log backups performed since the differential backup.

Differential backups are most beneficial under the following circumstances:

• A relatively small portion of the data in the database has changed since the last database backup. Differential database backups are most efficient if the same data is modified frequently.
• You are using the Simple Recovery model, which does not permit Transaction log backups, and you want to perform backups more frequently than is practical for full database backups.
• You are using the Full or Bulk-Logged Recovery model and want to minimize the time it takes to replay Transaction log backups when restoring a database.

Note: After you have modified the structure or configuration of the database (for example, by adding more data or log files or changing the recovery model), you must perform a full database backup before performing a differential or Transaction log backup. For more information, refer to Required Full Backups.