An online backup lets you back up the database while it is in use. You must use PROBKUP to perform online backups. Perform an online backup if the database cannot be taken offline long enough to perform an offline backup. You can perform both full and incremental online backups.
When deciding whether to use online backups, consider the following:
You cannot perform an online backup on a system running in single-user mode.
If you have enabled after-imaging, when you perform an online backup of a database, the database engine automatically switches over to the next AI file. Before you start an online backup, you must make sure that the next AI file is empty. If the file is not empty, PROBKUP aborts and notifies you that it cannot switch to the new file. For information about after-imaging, see After-imaging.
If you want to enable after-imaging while your database is online, you must perform a full online backup. The resulting backup is the baseline for applying after-image extents. For more information about enabling after-imaging, see the Enabling after-imaging online on page 208.
When you begin an online backup, database activity pauses until the backup header is written. Make sure that your backup media is properly prepared before issuing the PROBKUP command in order to minimize the duration of the pause. Until the database engine writes the header information, you cannot update the database. If you use more than one volume to back up the database, there is a similar delay each time you switch volumes.
You cannot use the PROBKUP parameters Scan (-scan) or Estimate (-estimate) for online backups.
You cannot perform an online backup on a system running in single-user mode.