Backups you schedule on a regular basis – daily, weekly, monthly, or at whatever interval is convenient for your application – can be full backups or incremental backups. The -n option is used to perform incremental backups (the ‘n’ stands for newer than). It tells BRU to save only files that were created or modified after the date specified as a parameter. By default, it will cause BRU to only save files that were modified (or the inode status changed) after the date specified as a parameter. The default mode check the modification time and the status (inode) change time. If either time is greater than the specified date, the file will be selected for backup. To change the default comparison method (i.e. compare with modification time only), use the date type modifier example
bru -c0n 7-DEC-94,m
If you have a large number of files to back up, you can save time by performing incremental backups, for example, on a daily basis, and then running a weekly full backup. This way, only the files that changed since your last full backup will be archived during the week. Depending on your supply of backup tapes, you can then consider reusing an old backup tape from two or three weeks ago for a given weekly backup. Once a month you may want to do a full backup of all files and save these archives virtually indefinitely.
The frequency with which you perform backups, and how long you preserve them, depends on how far back you think users may need to retrieve earlier versions of files. This decision will depend on your system and your needs.