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LOG SWITCH CHECK POINTS [message #599893]

Wed, 30 October 2013 00:55

rsb.oracle
Messages: 37
Registered: April 2013
Location: Chennai

Member

LOG SWITCH CHECK POINT - IS this true ?

Quote:

Writes the contents of the dirty buffers whose information is protected by a redo log to the database.

Thanks .

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Re: LOG SWITCH CHECK POINTS [message #599896 is a reply to message #599893]

Wed, 30 October 2013 02:13

John Watson
Messages: 8976
Registered: January 2010
Location: Global Village

Senior Member

Yes, if it happens. But it usually does not happen. In releases < 8.1, a log switch forced a full check point. In releases >= 8.1, it does not. If the next group to be used is still ACTIVE, then you will get log switch checkpoint (and a checkpoint incomplete message in the alert log) to make the log inactive so that LGWR can witch into it, but this should not happen if you have enough groups.
--
update: You quoted that sentence. From where did you copy it?

[Updated on: Wed, 30 October 2013 02:16]

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Re: LOG SWITCH CHECK POINTS [message #599897 is a reply to message #599896]

Wed, 30 October 2013 02:24

rsb.oracle
Messages: 37
Registered: April 2013
Location: Chennai

Member

Thanks John

I am using 10g and going to use 11g .

I have more than one redo log group i mean 3 group.

Code: [Select all] [Show/ hide]

If we use higher versions like 10g or 11g -  my quetion is not required , am i right ?

I have two questions :

1) What happens internally when the we issue alter database end backup ??
2) where does the extra redo goes ? and how does the synchronization takes place internally ?

Please reply.

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Re: LOG SWITCH CHECK POINTS [message #599898 is a reply to message #599897]

Wed, 30 October 2013 02:31

John Watson
Messages: 8976
Registered: January 2010
Location: Global Village

Senior Member

If you have whole series of questions, it would be better to attend a course or read some books. What are you trying to achieve? Way have these questions arisen?

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Re: LOG SWITCH CHECK POINTS [message #599899 is a reply to message #599897]

Wed, 30 October 2013 02:31

rsb.oracle
Messages: 37
Registered: April 2013
Location: Chennai

Member

Hi john;

You quoted that sentence. From where did you copy it?

Here .. http://oracleinaction.com/checkpoints/

Whenever dirty blocks are written to datafiles, it allows oracle
to reuse a redo log : A redo log can't be reused until DBWR writes all the dirty blocks protected by that logfile to disk.
If we attempt to reuse it before DBWR has finished its checkpoint,
we get the following message in alert log : Checkpoint not complete.

[Updated on: Wed, 30 October 2013 02:31]

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Re: LOG SWITCH CHECK POINTS [message #599901 is a reply to message #599899]

Wed, 30 October 2013 02:35

Michel Cadot
Messages: 68757
Registered: March 2007
Location: Saint-Maur, France, https...

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All these questions are answered and explained in Database Concepts.

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Re: LOG SWITCH CHECK POINTS [message #599902 is a reply to message #599898]

Wed, 30 October 2013 02:35

rsb.oracle
Messages: 37
Registered: April 2013
Location: Chennai

Member

Thanks.

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Re: LOG SWITCH CHECK POINTS [message #599904 is a reply to message #599899]

Wed, 30 October 2013 02:41

John Watson
Messages: 8976
Registered: January 2010
Location: Global Village

Senior Member

The author of that website is not always correct, and also steals material from others. Some has been stolen from me, as I pointed out here, http://www.orafaq.com/node/2824#comment-6890
I would not trust everything you read there, though the article to which you refer does appear to be correct: it my have been plagiarized from a reputable source.

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Re: LOG SWITCH CHECK POINTS [message #599905 is a reply to message #599904]

Wed, 30 October 2013 02:43

rsb.oracle
Messages: 37
Registered: April 2013
Location: Chennai

Member

Hi john ;

If you dont mind , can i get answer ?

1) What happens internally when the we issue alter database end backup ??
2) where does the extra redo goes ? and how does the synchronization takes place internally ?

[Updated on: Wed, 30 October 2013 02:44]

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Re: LOG SWITCH CHECK POINTS [message #599907 is a reply to message #599905]

Wed, 30 October 2013 02:50

Michel Cadot
Messages: 68757
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Location: Saint-Maur, France, https...

Senior Member
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1) Nothing special, just a flag set to off
2) In the redo logs; which synchronization?

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Re: LOG SWITCH CHECK POINTS [message #599908 is a reply to message #599904]

Wed, 30 October 2013 02:50

Littlefoot
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Registered: June 2005
Location: Croatia, Europe

Senior Member
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12c: PERFORMANCE ISSUE WITH IN-DATABASE ARCHIVING on that website does mention you, John:
Anju Garg

... But this feature you could also give problems with performance as pointed out by John Watson (http://www.orafaq.com/node/2824).

Does it settle problems with
John

I also noticed that you have not credited me with pointing out the problem and providing the solution. This is plagiarism.

(True, I didn't read all of these word-to-word, so I might be wrong).

[Updated on: Wed, 30 October 2013 02:50]

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Re: LOG SWITCH CHECK POINTS [message #599911 is a reply to message #599907]

Wed, 30 October 2013 03:02

rsb.oracle
Messages: 37
Registered: April 2013
Location: Chennai

Member

Hi michel ;

Are you able to catch my question ?

Consder user is updating table.

Quote:

When we issue , alter database begin backup ,

- more redo is generated here .

Quote:

when we issue alter database end backup ?

- The redos are written by LGWR from RLBC to Redo log group files.

All updated information - how it was synchronized ? what happens internally ?

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Re: LOG SWITCH CHECK POINTS [message #599912 is a reply to message #599908]

Wed, 30 October 2013 03:15

John Watson
Messages: 8976
Registered: January 2010
Location: Global Village

Senior Member

Littlefoot wrote on Wed, 30 October 2013 07:50

12c: PERFORMANCE ISSUE WITH IN-DATABASE ARCHIVING on that website does mention you, John:
Anju Garg

... But this feature you could also give problems with performance as pointed out by John Watson (http://www.orafaq.com/node/2824).

Does it settle problems with
John

I also noticed that you have not credited me with pointing out the problem and providing the solution. This is plagiarism.

(True, I didn't read all of these word-to-word, so I might be wrong).

That was added after I complained Smile

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Re: LOG SWITCH CHECK POINTS [message #599915 is a reply to message #599911]

Wed, 30 October 2013 03:25

Michel Cadot
Messages: 68757
Registered: March 2007
Location: Saint-Maur, France, https...

Senior Member
Account Moderator

rsb.oracle wrote on Wed, 30 October 2013 09:02

Hi michel ;

Are you able to catch my question ?

Consder user is updating table.

Quote:
When we issue , alter database begin backup ,

- more redo is generated here .

Quote:
when we issue alter database end backup ?

- The redos are written by LGWR from RLBC to Redo log group files.

All updated information - how it was synchronized ? what happens internally ?

The information you read are wrong or partially incorrect, please DO read the book I pointed you too it is explained in details and will fix your current wrong understanding.

Quote:

more redo is generated here .

This is a general statement and may or may not apply to your update statement. Only the first update of a block generates more redo (as explained in the book I pointed you too).

Quote:

The redos are written by LGWR from RLBC to Redo log group files.

In the same way than with a commit. Nothing special (see the book I pointed you too).

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Re: LOG SWITCH CHECK POINTS [message #599916 is a reply to message #599912]

Wed, 30 October 2013 03:28

Littlefoot
Messages: 21823
Registered: June 2005
Location: Croatia, Europe

Senior Member
Account Moderator

John

That was added after I complained

I see; well, he could have ignored you. There's justice out there after all (but sometimes it is slow) /forum/fa/1601/0/

[Updated on: Wed, 30 October 2013 03:28]

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