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smon and instance recovery [message #331719] Fri, 04 July 2008 23:43 Go to next message
varu123
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During startup,SMON performs instance recovery.
It applies the redo. My question is does it apply the redo directly to datafiles or in the buffer cache thus generating the dirty blocks that are written by DBWR?
Re: smon and instance recovery [message #331720 is a reply to message #331719] Fri, 04 July 2008 23:51 Go to previous messageGo to next message
BlackSwan
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varu123 wrote on Fri, 04 July 2008 21:43
During startup,SMON performs instance recovery.
It applies the redo. My question is does it apply the redo directly to datafiles or in the buffer cache thus generating the dirty blocks that are written by DBWR?


If/when doing INSTANCE RECOVERY, how is anything in buffer cache?

IMO, SGA is empty upon instance start!
Re: smon and instance recovery [message #331722 is a reply to message #331719] Sat, 05 July 2008 00:08 Go to previous messageGo to next message
varu123
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SGA is allocated in nomount state itself.
Instance recovery starts when oracle signalls "ALTER DATABASE OPEN ".
So, SGA is suppose is not empty but allocated.
Re: smon and instance recovery [message #331724 is a reply to message #331719] Sat, 05 July 2008 00:13 Go to previous messageGo to next message
BlackSwan
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When system reboots, what populates RAM with what "data"?
After system reboot, how/what does SMON have for actual & valid data and from where?
Re: smon and instance recovery [message #331849 is a reply to message #331719] Sun, 06 July 2008 01:01 Go to previous messageGo to next message
varu123
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Upon every instance startup SMON checks the SCN in the datafiles headers and in the control file headers for any inconsistency.

In the case of instance/crash recovery,it applies redo.
But Does it applies the redo directly in the datafiles bypassing buffer cache or first in buffer cache and from there DBWR finishes the job?


Re: smon and instance recovery [message #333714 is a reply to message #331719] Mon, 14 July 2008 04:10 Go to previous messageGo to next message
malikjee
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Registered: May 2007
Location: lahore
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Hi all!
I have read in documents that in above situation redo logs are directly applies to the datafiles ,
All these operations are dynamicly bypasses buffer cache by DBWR process to fininsh its job.

Best regards,
Malik
Re: smon and instance recovery [message #333728 is a reply to message #333714] Mon, 14 July 2008 04:59 Go to previous messageGo to next message
Michel Cadot
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Quote:
I have read in documents

Which ones?
Should we trust you?
Should we trust what you read?

Regards
Michel
Re: smon and instance recovery [message #333734 is a reply to message #331719] Mon, 14 July 2008 05:14 Go to previous messageGo to next message
malikjee
Messages: 80
Registered: May 2007
Location: lahore
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HI again!

Mr Michel, I dont have exactly remember that in whitch docs I have read that I am sure about I have said.But if you not trust me that go ahead and keep continue your reasearch about your doubt.........
best regards;
Malik
Re: smon and instance recovery [message #337721 is a reply to message #333734] Thu, 31 July 2008 18:54 Go to previous messageGo to next message
sunil_v_mishra
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Instance and crash recovery are the automatic application of redo log to records Oracle data blocks after a crash or system failure. During normal operation, if an instance is shut down cleanly (as when using a SHUTDOWN IMMEDIATE statement), rather than terminated abnormally, then the in-memory changes that have not already been written to the datafiles on disk are written to disk as part of the checkpoint performed during shutdown.

However, if a single instance database crashes or if all instances of an Oracle Real Application Cluster configuration crash, then Oracle performs crash recovery at the next startup. If one or more instances of an Oracle Real Application Cluster configuration crash, then a surviving instance performs instance recovery automatically. Instance and crash recovery occur in two steps: cache recovery followed by transaction recovery.

The database can be opened as soon as cache recovery completes, so improving the performance of cache recovery is important for increasing availability.

1. What is cache recovery?
Cache Recovery (Rolling Forward)
During the cache recovery step, Oracle applies all committed and uncommitted changes in the redo log files to the affected data blocks. The work required for cache recovery processing is proportional to the rate of change to the database (update transactions each second) and the time between checkpoints.

3. What is transaction recovery?
Transaction Recovery (Rolling Back)
To make the database consistent, the changes that were not committed at the time of the crash must be undone (in other words, rolled back). During the transaction recovery step, Oracle applies the rollback segments to undo the uncommitted changes.
Re: smon and instance recovery [message #337762 is a reply to message #337721] Fri, 01 August 2008 01:19 Go to previous messageGo to next message
Michel Cadot
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Just a copy and paste of the documentation at http://download.oracle.com/docs/cd/B19306_01/backup.102/b14191/rcmtunin004.htm#sthref1104

What I think about this way of trying to acquire recognition by just plagiarize others is... (censored)

Regards
Michel
Re: smon and instance recovery [message #338055 is a reply to message #337762] Sat, 02 August 2008 16:40 Go to previous messageGo to next message
sunil_v_mishra
Messages: 506
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As per the question asked what I pasted was more than enough

Over all link contain many things... Laughing
Re: smon and instance recovery [message #338068 is a reply to message #338055] Sun, 03 August 2008 01:35 Go to previous messageGo to next message
Michel Cadot
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What you post is stupid.
The link is EXACTLY what you posted.
If OP wants to read more, why do you prevent him from doing so posting a small part?
Copy and paste the doc if you want but above all and before post the link.
Anyway, what is obvious is that you just try to acquire recognition by copying other works; this is what all your posts show (at least those that contain something more than empty sentences ornamented with smileys). Grin

Regards
Michel
Re: smon and instance recovery [message #338100 is a reply to message #338068] Sun, 03 August 2008 10:08 Go to previous messageGo to next message
sunil_v_mishra
Messages: 506
Registered: March 2005
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Michel I feel Its your assumption that original poster wants to read more, because if he wants to read more he would not ask specific question on orafaq... Wink..

When people ask any question on orafaq they are interested just answer to there question nothing more than that, they all know there is documentation and metalink, they need answer to the point of
their question

And personally i don't want OP to read more. If he/she want to read more than read documentation and if they do have right then can see metalink ...why do they come on orafaq Very Happy ?

Can you tell me who had written oracle documentation ?

For Most of question asked on orafaq you can give some link of oracle documentation or metalink

[Updated on: Sun, 03 August 2008 10:12]

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Re: smon and instance recovery [message #338106 is a reply to message #338100] Sun, 03 August 2008 10:50 Go to previous message
Michel Cadot
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Registered: March 2007
Location: Nanterre, France, http://...
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Quote:
Michel I feel Its your assumption that original poster wants to read more,

Wrong. He wants or not I don't care but I don't want to restrict what he can do.
Posting link -> he can or not read more
Posting extract -> he can just read the extract.
Conclusion...

Quote:
Can you tell me who had written oracle documentation ?

Which line? Very Happy

Quote:
For Most of question asked on orafaq you can give some link of oracle documentation or metalink

Right, and this is what I do.

Quote:
why do they come on orafaq?

Lazyness for most of them, this is obvious (for the questions that just require to read the doc).

Regards
Michel
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