rsona

 Profile Answers by rsona 

• Mar 2nd, 2011

 

Hello Ganesh,

Q : What is the use of archive log file?
A : It is used for Point In Time Database Instance Recovery.
    
Q : How will you apply archive log file?
A : Archive Log need to apply when you need to recover database.
     SQL> startup mount
     SQL> alter database recover
               <<-- Here database instance shall prompt you for reuired archive log file, you may perform Manual or AUTO recovery-->>

Q : How does archive log file helps to make backup consistent?
A : If database is in Archive Log Mode the only it is possibel to perform HOT (Online) Backup, however all transaction entries would be done in Redo File and eventually it will be written to Archive Log File, it also called  Archived Redo Log files.

Hence by backing up Datafiles/Redo Log Files/Control Files and Archived redo Log Files you can have a consistent backup.

Only in caseof Cold backup you dont reuire Archive Redo Log files as database instance is down whiler performing Cold backup.

For more details you may refer -

http://download.oracle.com/docs/cd/B19306_01/server.102/b14357/ch12007.htm

Hope this helps.

Best Regards,
Rohit.

ARUN BHUKKER

 Profile Answers by ARUN BHUKKER 

• Oct 19th, 2012

 

A Archive log file is used to archive the filled redo log files. and used in recovery.

It is used in recovery but not in instance recovery.
Rest it is used to make database consistent after recovery by matching header of data file and control file checkpoint information.