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log switching in hot backup [message #194472] Fri, 22 September 2006 05:45 Go to next message
itcontrax
Messages: 1
Registered: September 2006
Junior Member
Can someone explain why a log switch is required after a hot backup? The general explations I have read are to ensure that all scn numbers are consistant in order to ensure that the backup you have just taken is restorable and that the end backup marker needs to be archived? Surely the backup will be restorable without a log switch as all the info oracle requires is in the current redo log file? The only scenario I can imagine a log switch being any use for is in a situation where you lose your current online redo log before the backup information has been written to archive. What am I missing?. Any help appreciated.
Re: log switching in hot backup [message #194481 is a reply to message #194472] Fri, 22 September 2006 06:20 Go to previous messageGo to next message
Mahesh Rajendran
Messages: 10672
Registered: March 2002
Location: oracleDocoVille
Senior Member
Account Moderator
>>Can someone explain why a log switch is required after a hot backup?
Is there a link in documentation that would state this?
Re: log switching in hot backup [message #196032 is a reply to message #194472] Tue, 03 October 2006 14:55 Go to previous messageGo to next message
parthokonar
Messages: 17
Registered: September 2006
Location: india
Junior Member
Once the backup is complete, Oracle records the current database checkpoint in the file headers.

In order for this to be possible, we need to back up the redo logs that were being written while the hot backup was being performed. If a log switch had occurred, the archiver would have copied the online redo log file to the archive destination and started a new file. To get all of the relevant redo information, we need to force a log switch and then back up all of the files that are sitting in the archive destination.

Re: log switching in hot backup [message #196161 is a reply to message #196032] Wed, 04 October 2006 06:29 Go to previous messageGo to next message
pareshr
Messages: 18
Registered: August 2006
Location: Ahmedabad
Junior Member
Hi all,

parthokonar is true. Actually reason is when we put datafile and tablespace in backup mode. It freez the datafile header. So all the changed blocks of that datafile are stored in log file... So those changes of recorded in log needs to apply to datafile. That log applies immediately when we do log switch.

Thnks,
Paresh Rupareliya
Re: log switching in hot backup [message #196319 is a reply to message #194472] Thu, 05 October 2006 00:19 Go to previous message
gkrishn
Messages: 506
Registered: December 2005
Location: Putty a dark screen
Senior Member
To itcontrax :
try to recover a database(point in time) with hot backup taken.Database will exepct some more logfiles though u have all datafiles taken during hotbackup .. so it will ask you for more logfiles(atleast it require 1 )
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