Backup and Recovery - Backup Mode Redo Generation

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Backup Mode Redo Generation

Why more redos are generated when the database is in begin backup mode?

Total Answers and Comments: 3

Last Update: September 16, 2009 Asked by: md.sarf

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Submitted by: oracleofdelphi

During begin backup mode datafile headers get freezed and as a result row information cannot be retrieved as a result the entire block is copied to redo logs as a result more redo generated and more log switch and in turn more archive logs.

Above answer was rated as good by the following members:
compusa321

August 19, 2009 02:43:39

harshljica

Member Since: August 2009 Contribution: 3

RE: Backup Mode Redo Generation

During execution of begin backup mode all the datafiles header are stuck up.
During Begin backup mode the scn no ckpt no and log sequence no are not write in header of datafile so that more redo entries are generated.

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September 09, 2009 10:48:12

oracleofdelphi

Member Since: September 2009 Contribution: 6

RE: Backup Mode Redo Generation

During begin backup mode datafile headers get freezed and as a result row information cannot be retrieved as a result the entire block is copied to redo logs as a result more redo generated and more log switch and in turn more archive logs.

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1 0

Overall Rating: +1

September 13, 2009 09:24:30

atifkhan8686

Member Since: September 2009 Contribution: 1

RE: Backup Mode Redo Generation

As soon as you issue

SQL> Alter database begin backup;

This command freezes the datafile headers as well as controlfile headers but the headers of redolog files are free.

Hence if any of the transaction is performed after the online backup command. The SCN's are recorded in the header of redolog files but in the header of datafile and controlfiles header hence extra redo's are generated.

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