An incremental backup stores all files that have changed since the last full, differential or incremental backup. The advantage of an incremental backup is that it takes the least time to complete. However, during a restore operation, each incremental backup is processed, which could result in a lengthy restore job.
Type
Clear archive bit
If checked, the application will remove the Archive flag of the files that were added to the backup. By default Backup4all uses the current comparison criteria and the information from catalog file to detect if a file was modified or not since the last backup, which is more accurate than using only the Archive bit (as other backup programs do). However, if you want to backup files based only on the Archive bit attribute, you can change the comparison criteria from the Advanced->Backup window.
Limit maximum number of stored backups to
At each backup execution, a new backup number is created. In time backup numbers can grow. This option will ensure that the maximum number of stored backups will not exceed the specified number. The system will delete some of the older backup numbers, keeping the recent ones and ensuring backup integrity. The minimum number of backups you can store is 3.
Merge stored backups to maintain the maximum limit
This option is enabled when the first option is set. This option is important when you do not want to lose intermediate backups. The system first tries to delete older backup numbers. If this is not possible (because it will damage backup integrity) then the system will merge several backup numbers into one. Merging backup numbers is time consuming, because the zip files for the merged backup number are recreated.
These two options will not be taken into consideration if you make your backups on removable media.
Let's take an example. Suppose there is an incremental backup with 10 backups: backup number 1 is the oldest (full) and backup number 10 is the newest. Backup numbers 2-10 are all incremental.
If you limit the number of stored backups to 5 and do not check the Merge stored backup to maintain the maximum limit option, the system will first make a new incremental backup (11) based on the first full backup and then it will delete backup numbers from 2-10. Only 2 backup numbers will remain: 1 and 11. In this case backup number 11 will contain all the differences since the first full. So the maximum limit (5) is respected, but you could lose intermediate file versions. For example a file could have versions in backup number 2, 8 and 10, but only the version from 10 will be present in backup number 11. If the file would have changed since backup number 10, then the new version would be added in backup number 11.
If you limit number of stored backups 5 and check the Merge stored backup to maintain the maximum limit option, the system will first make a new backup (11) with the differences since backup number 10 and then it will merge backup numbers 2-8 into backup number 8, keeping the most recent version of each file present in those backup numbers. Finally the system will keep backup numbers 1, 8, 9, 10, 11 (a total of five as you configured).
Incremental
Make full backup when all increments exceed % of full backup size
In time, the size of the incremental can outgrow the full version. For maximum efficiency, the size of the incremental should be kept as small as possible. This option will trigger the creation of a full backup when a certain percentage of the full backup will be exceeded (default is 50%).
Make full backup when all increments exceed
If this is checked, Backup4all will trigger the creation of a full backup when that custom size is reached (default is 1 megabyte).
Zip settings
Encryption
This feature provides an easy way to encrypt the zip files that are created. Files in zip can be extracted with third party zip managers if the user enters the same password as in the Encryption Settings window. Note that when using AES encryption, some older zip managers don't recognize this type of encryption.
Advanced
This button will open a new window where you can set the zip compression level, customized zip file names and zip file splitting policy. Read more on Zip Advanced Settings