SQL Backup Master uses this folder to store all transient database backups before they are uploaded to their final backup destination(s). By default, SQL Backup Master will use the local Windows temp folder for this setting.
One reason you may wish to change this setting is to support remote backups, in which case you will likely need to configure it with a shared UNC path. For more information, see the remote backups help topic.
Also please note that SQL Backup master compresses database files contained within this folder. If you find that the compression of large database files is creating too much local file system I/O, you may wish to consider mapping the temporary backup folder to another drive (e.g. a different local drive on a separate I/O channel, an external drive, a network drive, etc.).
Important: We strongly recommend against the use of mapped network drive letters when assigning the temporary backup folder location (for security and portability reasons). Instead, please consider using UNC paths in the form of "\\server\share" (without the quotes).
By default, SQL Backup Master will automatically delete old differential and transaction log backup files after each full or differential backup job executes. This is done to conserve storage space.
Since each differential backup contains all the data changed since the last full backup, there's generally no need to keep previous differential backup files around.
Similarly, transaction log backups are generally only used to restore to some point after the latest full or differential backup.
You're also given the option to retain the most recent full backup (for each database being backed up) during file cleanup operations, regardless of the age of said backup. For example, if you configure a backup destination to remove old backup files after 7 days, this option will retain the most recent full backup file even if it's older than that. This can be useful in cases where you want to ensure that a full backup is always present in order to support recovery of differential or transaction log backups.
Important: Be sure that your backup destination has sufficient storage space to accommodate whatever data retention options you choose.