A copy-only backup is a backup, which is independent of the sequence of regular Full backup.
When you run a log backup after a copy-only full backup, the log backup is automatically chained to the copy-only full backup and follows the retention rules of the copy-only full backup. If there are any missing logs during the log backup, the next backup operation is automatically converted to a regular full backup.
This type of backup can be performed for a special purpose and does not affect the overall backup and restore procedures. It applies to Full backups only.
From the navigation pane, go to Protect > Databases.
The Instances page appears.
Click the instance.
The instance page appears.
On the Overview tab, under Subclients, in the row for the subclient that you want to back up, click the action button , and then select Back up.
The Select backup level dialog box appears.
Under Advanced options, move the Copy-Only toggle key to the right.