RE: no archivelog incomplete recovery?
- From: "Elliott, Patrick" <patrick.elliott@xxxxxxxxxxxxx>
- To: "Elliott, Patrick" <patrick.elliott@xxxxxxxxxxxxx>, "john40855@xxxxxxxxx" <john40855@xxxxxxxxx>, Hemant K Chitale <hkchital@xxxxxxxxxxxxxx>
- Date: Mon, 7 Jul 2008 13:42:53 -0500
When I think about it...
If you check the v$loghist table and see that the number of log switches since
the last full backup is less than the total number of online redo logs, then
you would know that the below situation would apply.
Pat
________________________________
From: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx] On
Behalf Of Elliott, Patrick
Sent: Monday, July 07, 2008 1:31 PM
To: john40855@xxxxxxxxx; Hemant K Chitale
Cc: oracle-l@xxxxxxxxxxxxx
Subject: RE: no archivelog incomplete recovery?
This isn't entirely true. If you are lucky, and the online redo logs were
never overwritten since the last cold backup, then you could apply the inactive
archive logs up to just before the lost active one. During the recovery you
would specify the full path to the online redologs that need to be applied.
This will work in either archivelog or noarchivelog mode. In the case where
your backup includes the online archive logs, it might be a good idea to save
the unbroken online redologs just in case they can be used. You might get
lucky again and the online logs may have only been overwritten once.
Of course the above scenario will only work with a very quiet database. 99.99%
of the databases would not be able to use this.
Pat
________________________________
From: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx] On
Behalf Of John Smith
Sent: Monday, July 07, 2008 11:50 AM
To: Hemant K Chitale
Cc: oracle-l@xxxxxxxxxxxxx
Subject: Re: no archivelog incomplete recovery?
So in effect, it is a trick question because the recovery will only be to the
state at the last full backup, even if they do call it 'recovery'? Since no
archived logs will be available?
On Mon, Jul 7, 2008 at 10:01 AM, Hemant K Chitale
<hkchital@xxxxxxxxxxxxxx<mailto:hkchital@xxxxxxxxxxxxxx>> wrote:
The keywords
"how to recover from a lost active online redo log in noarchivelog mode."
is ACTIVE !
As the database is in NOARCHIVELOG, the only way a redo log could be ACTIVE
would be if a Checkpoint hasn't been completed.
[had the lost online redo log been an Inactive one, you wouldn't have needed to
do a Restore AT ALL, provided that you knew what to do !].
The only option is to Restore the last Consistent Backup. IF the Consistent
Backup included the Online Redo Logs, then you do not need to RESETLOGS. If ,
however, the DBA had followed the advice of most "experts" and the
documentation and did not backup his Online Redo Logs [in his Consistent Cold
Backup of a NoArchiveLog database] you would HAVE to do a RESETLOGS.
(having said that, I guess it should be obvious that I don't agree with most
"experts" and the documentation that you should NEVER backup the Online Redo
Logs. This is one of the scenarios where a backup of the Online Redo Logs [in
a Consistent Cold Backup] would make an OPEN less "uncomfortable" !
But coming back to the scenario provided in your test : Although a RESETLOGS
would be adviced, a RECOVER DATABASE wouldn't be needed at all.
The sequence would be :
a. Restore Consistent Backup.
b. Verify if it included Online Redo Logs. If if did not include the Online
Redo Logs, go to step e.
c. STARTUP {ie, the same as STARTUP MOUNT; ALTER DATABASE OPEN (normal)}
in sqlplus / as sysdba
d. exit from sqlplus prompt and get a pay raise
e. STARTUP MOUNT ; ALTER DATABASE OPEN RESETLOGS in sqlplus / as sysdba
Hemant K Chitale
At 07:57 AM Monday, John Smith wrote:
I am studying for the OCP, and one of the practice test questions is how to
recover from a lost active online redo log in noarchivelog mode. the answer
they give is to restore a consistent backup, startup in mount mode, perform a
cancel based recovery, and open with resetlogs.
Is that answer correct? I didnt think you could do a recovery if you arent in
archivelog mode.
Hemant K Chitale
http://hemantoracledba.blogspot.com
"A 'No' uttered from the deepest conviction is better than a 'Yes' merely
uttered to please, or worse, to avoid trouble."
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