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About REDO LOG FILE [message #438996]

Wed, 13 January 2010 09:29

muktha_22
Messages: 527
Registered: December 2009

Senior Member

Hello all,
Thanks for you help. Here is one more doubt needs to be clarified.

Case 1:
I have taken a backup of with 100 Rows in a table. Yesterday

Case 2:
Due to some problem, that particular Datafile got missed/Corrupted.

Case 3:
So Now I'm Restoring & Recovering that DATAFILE. So I got all that data's back.

Question:
How the SCN Number from the DATAFILE's header and CONTROLFILE.

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Re: How the Datafile & Controlfile get SYNC. [message #438998 is a reply to message #438996]

Wed, 13 January 2010 09:47

BlackSwan
Messages: 26766
Registered: January 2009
Location: SoCal

Senior Member

SQL> desc v$database
 Name					   Null?    Type
 ----------------------------------------- -------- ----------------------------
 DBID						    NUMBER
 NAME						    VARCHAR2(9)
 CREATED					    DATE
 RESETLOGS_CHANGE#				    NUMBER
 RESETLOGS_TIME 				    DATE
 PRIOR_RESETLOGS_CHANGE#			    NUMBER
 PRIOR_RESETLOGS_TIME				    DATE
 LOG_MODE					    VARCHAR2(12)
 CHECKPOINT_CHANGE#				    NUMBER
 ARCHIVE_CHANGE#				    NUMBER
 CONTROLFILE_TYPE				    VARCHAR2(7)
 CONTROLFILE_CREATED				    DATE
 CONTROLFILE_SEQUENCE#				    NUMBER
 CONTROLFILE_CHANGE#				    NUMBER
 CONTROLFILE_TIME				    DATE
 OPEN_RESETLOGS 				    VARCHAR2(11)
 VERSION_TIME					    DATE
 OPEN_MODE					    VARCHAR2(10)
 PROTECTION_MODE				    VARCHAR2(20)
 PROTECTION_LEVEL				    VARCHAR2(20)
 REMOTE_ARCHIVE 				    VARCHAR2(8)
 ACTIVATION#					    NUMBER
 SWITCHOVER#					    NUMBER
 DATABASE_ROLE					    VARCHAR2(16)
 ARCHIVELOG_CHANGE#				    NUMBER
 ARCHIVELOG_COMPRESSION 			    VARCHAR2(8)
 SWITCHOVER_STATUS				    VARCHAR2(20)
 DATAGUARD_BROKER				    VARCHAR2(8)
 GUARD_STATUS					    VARCHAR2(7)
 SUPPLEMENTAL_LOG_DATA_MIN			    VARCHAR2(8)
 SUPPLEMENTAL_LOG_DATA_PK			    VARCHAR2(3)
 SUPPLEMENTAL_LOG_DATA_UI			    VARCHAR2(3)
 FORCE_LOGGING					    VARCHAR2(3)
 PLATFORM_ID					    NUMBER
 PLATFORM_NAME					    VARCHAR2(101)
 RECOVERY_TARGET_INCARNATION#			    NUMBER
 LAST_OPEN_INCARNATION# 			    NUMBER
 CURRENT_SCN					    NUMBER
 FLASHBACK_ON					    VARCHAR2(18)
 SUPPLEMENTAL_LOG_DATA_FK			    VARCHAR2(3)
 SUPPLEMENTAL_LOG_DATA_ALL			    VARCHAR2(3)
 DB_UNIQUE_NAME 				    VARCHAR2(30)
 STANDBY_BECAME_PRIMARY_SCN			    NUMBER
 FS_FAILOVER_STATUS				    VARCHAR2(21)
 FS_FAILOVER_CURRENT_TARGET			    VARCHAR2(30)
 FS_FAILOVER_THRESHOLD				    NUMBER
 FS_FAILOVER_OBSERVER_PRESENT			    VARCHAR2(7)
 FS_FAILOVER_OBSERVER_HOST			    VARCHAR2(512)

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About REDO LOG FILE [message #438999 is a reply to message #438996]

Wed, 13 January 2010 09:48

muktha_22
Messages: 527
Registered: December 2009

Senior Member

Hi All,
Need a clarification on below.

Step 1:
I have taken a backup of table with 100 ROWS.

Step 2:
Now I am inserting 10 Rows.

Step 3:
By mistakenly, The particular Table's Datafile got corrupted/Missed.

Step 4:
Now I'm able to get back all those datas which is added recently after the backup. IT means total rows are 110.

Question:
How the inserted rows got placed back to that Datafile?
(Because, only the DELETED & UPDATED data will be stored in to the Online Redo log files, isn't it).

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Re: About REDO LOG FILE [message #439001 is a reply to message #438999]

Wed, 13 January 2010 10:00

Michel Cadot
Messages: 68665
Registered: March 2007
Location: Nanterre, France, http://...

Senior Member
Account Moderator

The redo logs are applied in the same way the final step (block modification) of the original actions where executed.

Regards
Michel

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Re: About REDO LOG FILE [message #439009 is a reply to message #438999]

Wed, 13 January 2010 10:42

JRowbottom
Messages: 5933
Registered: June 2006
Location: Sunny North Yorkshire, ho...

Senior Member

Quote:

How the inserted rows got placed back to that Datafile?
(Because, only the DELETED & UPDATED data will be stored in to the Online Redo log files, isn't it).

No.
All changes to the data, including Inserts (among other things) are written to the Redo Logs.

There are a couple of exceptions to this (Temporary Tables, and NOLOGING operations) but in general you don't need to worry about them.

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