September 5, 2001 at 2:42 am
Hi all
I am about to run some tests to determine the "24x7" hr'ness of the database during a FULL backup. From what ive read to date SQL*Server uses fuzzy backups where it will serially backup pages to the dump device. I believe it stored away the last committed transaction id at the start of the backup and back's up the entire DB, and subsequently uses this id as its "recovery" point for one of a better word.
Therefore, ongoing transactions can run without error BUT they will NOT be included in the FULL backup. So log backups after the fact will pick them up.
Any comments on this? I will post my findings when ive completed testing...
Cheers
Chris
Chris Kempster
www.chriskempster.com
Author of "SQL Server Backup, Recovery & Troubleshooting"
Author of "SQL Server 2k for the Oracle DBA"
September 5, 2001 at 10:23 am
this is (theoretically) correct. The way backups work, is that once you start, you want a backup of every page in it's state when the backup STARTS. This way you have integrity. If it backed up each page as it came to it and allowed changes, this could result in a backup that was not intact (based on RI). The fuzziness allows the backup to continue while transactions occur.
Steve Jones
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