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alter tablespace begin backup [message #405878] Sat, 30 May 2009 19:00 Go to next message
tjay
Messages: 37
Registered: September 2008
Member
Hi

Assume user managed backup, not rman.

Why should we copy the datafiles after
"alter tablespace begin backup"..

What does this statement do?
Does it locks the datafiles to avoid IO,or avoid increasing checkpoint SCN of the datafile.

Re: alter tablespace begin backup [message #405879 is a reply to message #405878] Sat, 30 May 2009 19:11 Go to previous messageGo to next message
BlackSwan
Messages: 25036
Registered: January 2009
Location: SoCal
Senior Member
>Why should we copy the datafiles after
>alter tablespace begin backup"
>What does this statement do?

When all else fails, you should Read The Fine Manual (RTFM) as shown in URL below.

http://download.oracle.com/docs/cd/B19306_01/server.102/b14200/statements_3002.htm#i2093894

It causes whole database block to be written to the REDO log files instead of just changed row while doing DML.
This allows consistent recovery to be achieved during DB restore.
Re: alter tablespace begin backup [message #405881 is a reply to message #405879] Sat, 30 May 2009 20:59 Go to previous messageGo to next message
tjay
Messages: 37
Registered: September 2008
Member
you explained very well
Re: alter tablespace begin backup [message #405884 is a reply to message #405881] Sun, 31 May 2009 01:11 Go to previous messageGo to next message
Michel Cadot
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Actually it is "It causes whole database block to be written to the REDO log files instead of just changed row while doing the first DML on the block after "begin backup", the subsequent ones are normal".
In addition, it freezes the tablespace datafiles header.

Regards
Michel
Re: alter tablespace begin backup [message #405891 is a reply to message #405884] Sun, 31 May 2009 03:20 Go to previous messageGo to next message
tjay
Messages: 37
Registered: September 2008
Member
During online backup:

"alter tablespace begin backup"

The checpoint scn of the datafiles do not change.
What is the main purpose of this?

and in this state I can perform transactions to the tablepsace.
Are these transactions recorded in redo(not in datafiles) and performed recovery after "alter tablespace end backup"

[Updated on: Sun, 31 May 2009 03:21]

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Re: alter tablespace begin backup [message #405901 is a reply to message #405891] Sun, 31 May 2009 09:34 Go to previous messageGo to next message
Michel Cadot
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Quote:
The checpoint scn of the datafiles do not change.
What is the main purpose of this?

To know when the latest safe write happened.

Quote:
Are these transactions recorded in redo(not in datafiles)

Nothing but the points I mentioned in my previous post.

Regards
Michel
Re: alter tablespace begin backup [message #405922 is a reply to message #405901] Sun, 31 May 2009 18:37 Go to previous messageGo to next message
tjay
Messages: 37
Registered: September 2008
Member
You told me that:

"It causes whole database block to be written to the REDO log"

After "alter tablespace end backup"
Does the info in redolog written to datafiles?(recovery)
Re: alter tablespace begin backup [message #405923 is a reply to message #405878] Sun, 31 May 2009 19:10 Go to previous messageGo to next message
BlackSwan
Messages: 25036
Registered: January 2009
Location: SoCal
Senior Member
>Does the info in redolog written to datafiles?(recovery)

What will it take to get you to follow Posting Guidelines as stated in URL below?
http://www.orafaq.com/forum/t/88153/0/

You are asking questions that are clearly answered by Reading The Fine Manuals found at http://tahiti.oracle.com

such as
http://download.oracle.com/docs/cd/B19306_01/server.102/b14220/index.htm#R
Re: alter tablespace begin backup [message #405924 is a reply to message #405923] Sun, 31 May 2009 20:23 Go to previous messageGo to next message
tjay
Messages: 37
Registered: September 2008
Member
You helped a lot dude.
Re: alter tablespace begin backup [message #405933 is a reply to message #405922] Mon, 01 June 2009 00:24 Go to previous message
Michel Cadot
Messages: 64103
Registered: March 2007
Location: Nanterre, France, http://...
Senior Member
Account Moderator
tjay wrote on Mon, 01 June 2009 01:37
You told me that:

"It causes whole database block to be written to the REDO log"

It does not mean the data are not *also* written to datafiles, they may be.
The ONLY points that change with "begin backup" are the 2 points I already mentioned (did I already say that?).

Regards
Michel

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