Editing Backup (section)

===Live data===
Files that are actively being updated present a challenge to back up. One way to back up live data is to temporarily [[quiesce]] them (e.g., close all files), take a "snapshot", and then resume live operations. At this point the snapshot can be backed up through normal methods.<ref name="CougiasTheBackup03Chapter11">{{cite book |chapter-url=https://books.google.com/books?id=eLviiTag5A0C&pg=PA360|title=The Backup Book: Disaster Recovery from Desktop to Data Center |chapter=Chapter 11: Open file backup for databases |author=Cougias, D.J. |author2=Heiberger, E.L. |author3=Koop, K. |publisher=Network Frontiers |pages=356–360 |year=2003 |isbn=0-9729039-0-9}}</ref> A [[Snapshot (computer storage)|snapshot]] is an instantaneous function of some filesystems that presents a copy of the filesystem as if it were frozen at a specific point in time, often by a [[copy-on-write]] mechanism. Snapshotting a file while it is being changed results in a corrupted file that is unusable. This is also the case across interrelated files, as may be found in a conventional database or in applications such as [[Microsoft Exchange Server]].<ref name="ComputerWeeklyCDPExplained" /> The term [[fuzzy backup]] can be used to describe a backup of live data that looks like it ran correctly, but does not represent the state of the data at a single point in time.<ref name="LiotineMission03">{{cite book |url=https://books.google.com/books?id=LecC2BhPPxMC&pg=PA244 |title=Mission-critical Network Planning |author=Liotine, M. |publisher=Artech House |page=244 |year=2003 |isbn=978-1-58053-559-5 |access-date=8 May 2018}}</ref>

Backup options for data files that cannot be or are not quiesced include:<ref name="deGuiseEnterprise09#3.4.7">{{cite book |url=https://books.google.com/books?id=2OtqvySBTu4C&pg=PA50 |title=Enterprise Systems Backup and Recovery: A Corporate Insurance Policy |author=de Guise, P. |publisher=CRC Press |pages=50–54 |year=2009 |isbn=978-1-4200-7639-4}}</ref>
*Open file backup: Many backup software applications undertake to back up open files in an internally consistent state.<ref name="HandyBackupOpenFileWindows">{{cite web |title=Open File Backup Software for Windows |url=https://www.handybackup.net/open-file-backup.shtml
   |website=Handy Backup |publisher=Novosoft LLC
   |access-date=29 November 2018 |date=8 November 2018}}</ref> Some applications simply check whether open files are in use and try again later.<ref name="CougiasTheBackup03Chapter11" /> Other applications exclude open files that are updated very frequently.<ref name="ArqTroubleshootingBackingUpOpen/lockedFiles">{{cite web |last1=Reitshamer |first1=Stefan |title=Troubleshooting backing up open/locked files on Windows |url=https://www.arqbackup.com/blog/troubleshooting-backing-up-openlocked-files-on-windows/ |website=Arq Blog
   |publisher=Haystack Software
   |access-date=29 November 2018 |date=5 July 2017 |at=Stefan Reitshamer is the principal developer of Arq}}</ref> Some [[High availability|low-availability]] interactive applications can be backed up via natural/induced pausing.
*Interrelated database files backup: Some interrelated database file systems offer a means to generate a "hot backup"<ref name="UWiscOracleBackups">{{cite web |last1=Boss |first1=Nina |title=Oracle Tips Session #3: Oracle Backups |url=http://www.wisc.edu/drmt/oratips/sess003.html#Hotbackup |archive-url=https://web.archive.org/web/20070302110933/http://www.wisc.edu/drmt/oratips/sess003.html#Hotbackup |url-status=dead |website=www.wisc.edu |publisher=University of Wisconsin |access-date=1 December 2018 |archive-date=2 March 2007 |date=10 December 1997}}</ref> of the database while it is online and usable. This may include a snapshot of the data files plus a snapshotted log of changes made while the backup is running. Upon a restore, the changes in the log files are applied to bring the copy of the database up to the point in time at which the initial backup ended.<ref name="ArcserveOracleWhatIsARCHIVE-LOG">{{cite web |title=What is ARCHIVE-LOG and NO-ARCHIVE-LOG mode in Oracle and the advantages & disadvantages of these modes? |url=https://support.arcserve.com/s/article/202080249?language=en_US |website=Arcserve Backup |publisher=Arcserve |access-date=29 November 2018 |date=27 September 2018}}</ref> Other low-availability interactive applications can be backed up via coordinated snapshots. However, [[High availability|genuinely-high-availability]] interactive applications can be only be backed up via Continuous Data Protection.