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Confusion about restoring controlfile without backup [message #477948]

Tue, 05 October 2010 06:08

indrajit2002
Messages: 53
Registered: November 2007
Location: INDIA

Member

Hi,
After creating a controlfile manually without any backup how the database goes to a consistent state? Because the newly created controlfile does not have the scn details as well as checkpoint information that the deleted controlfile had.
Also after restoring the controlfile is it needed to open the database in resetlogs mode? If not why?

Please help me to clear these confusions.

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Re: Confusion about restoring controlfile without backup [message #477950 is a reply to message #477948]

Tue, 05 October 2010 06:15

Michel Cadot
Messages: 68737
Registered: March 2007
Location: Saint-Maur, France, https...

Senior Member
Account Moderator

Why don't you just try it and see what happens.
In my opinion, control file synchronisation is done at open (resetlogs).

Regards
Michel

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Re: Confusion about restoring controlfile without backup [message #477958 is a reply to message #477950]

Tue, 05 October 2010 06:37

indrajit2002
Messages: 53
Registered: November 2007
Location: INDIA

Member

Thanks Michel. I have tried and seen that if you manually create the controlfile using the create controlfile script and then take the database in mount as well as open state subsequently you do not have to open it in resetlogs mode. That is why I am confused as to how the controlfile gets the information about the current thread checkpoints and archive log scn's.

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Re: Confusion about restoring controlfile without backup [message #477980 is a reply to message #477958]

Tue, 05 October 2010 08:37

Michel Cadot
Messages: 68737
Registered: March 2007
Location: Saint-Maur, France, https...

Senior Member
Account Moderator

Quote:

That is why I am confused as to how the controlfile gets the information about the current thread checkpoints and archive log scn's.

Checkpoint is taken from file headers.
SCN is taken from the last point you recover.

Regards
Michel

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Re: Confusion about restoring controlfile without backup [message #477984 is a reply to message #477980]

Tue, 05 October 2010 08:51

indrajit2002
Messages: 53
Registered: November 2007
Location: INDIA

Member

That means scn's are taken from the online redo log file right?

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Re: Confusion about restoring controlfile without backup [message #477988 is a reply to message #477984]

Tue, 05 October 2010 09:04

Michel Cadot
Messages: 68737
Registered: March 2007
Location: Saint-Maur, France, https...

Senior Member
Account Moderator

Yes.

Regards
Michel

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Re: Confusion about restoring controlfile without backup [message #477990 is a reply to message #477988]

Tue, 05 October 2010 09:16

indrajit2002
Messages: 53
Registered: November 2007
Location: INDIA

Member

Thanks Michel.

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Re: Confusion about restoring controlfile without backup [message #477998 is a reply to message #477958]

Tue, 05 October 2010 10:18

John Watson
Messages: 8965
Registered: January 2010
Location: Global Village

Senior Member

indrajit2002 wrote on Tue, 05 October 2010 06:37

I have tried and seen that if you manually create the controlfile using the create controlfile script and then take the database in mount as well as open state subsequently you do not have to open it in resetlogs mode.

Not true! I did think that following a controlfile restore or create, a resetlogs is always required - I tested it, and it is.
(I'm sure you weren't trying to deceive, but I always like to be precise)

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Re: Confusion about restoring controlfile without backup [message #478105 is a reply to message #477948]

Wed, 06 October 2010 05:20

indrajit2002
Messages: 53
Registered: November 2007
Location: INDIA

Member

No I am not trying to deceive. Just try the other way out. Delete all the controlfiles from your test database and create it manually using the 'Create Controlfile script' then issue alter database open. tell me what you get.

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Re: Confusion about restoring controlfile without backup [message #478117 is a reply to message #478105]

Wed, 06 October 2010 07:10

Michel Cadot
Messages: 68737
Registered: March 2007
Location: Saint-Maur, France, https...

Senior Member
Account Moderator

What don't you post (copy and paste) the test you made? Then we can all see what you do and get.

Regards
Michel

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Re: Confusion about restoring controlfile without backup [message #478118 is a reply to message #478117]

Wed, 06 October 2010 07:13

John Watson
Messages: 8965
Registered: January 2010
Location: Global Village

Senior Member

Just done it again, and I see that there is a dependency on the SET keyword of the CREATE DATABASE command. If I omit it, then the NORESETLOGS keyword comes into effect. Thanks, I didn't know that.

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