An incremental backup backs up the files that have changed or were created since the last incremental or full backup. Incremental Backup does this by backing up only files that have the archive bit set (which means that the file needs to be backed up, either a new file or a file which is modified). Incremental Backup is different from a full backup, because a full backup will back up any file that is selected because it does not use the archive bit to determine whether to back the file up or not. An incremental backup will back up whatever files you have selected that have the archive bit set. By using a combination of the full backup and incremental backup we can perform backups more efficiently by consuming less time and less storage space. To restore your backed up data, you need to restore the last full backup and then restore all the incremental backups order wise.
To view the archive bit in Windows 2003, right-click on the file and go to the properties. Once in the properties, click the Advanced button on the general tab. You will see the option that says “File is Ready for Archiving”. Whenever a new file is created or modified, Windows 2003 sets the archive bit.