I read " professional oracle programming 2005 " book.
http://arsamandish.com/dl/ebook/oracle/Professional%20Oracle%20Programming%202005.pdf On page number 4 , I snippet a text as here.
Redo Log Files :-
---------------
One of key features of a relational database is its ability to recover to a logically consistent state, even in
the event of a failure. Every relational database, including Oracle, uses a set of redo log files. These files
keep track of every interaction with the database. In the event of a database failure, an administrator can
recover the database by restoring the last backup and then applying the redo log files to replay user
interactions with the database.
Redo log files eventually fill up and roll over to start a new volume. You can set up Oracle to avoid writing
over existing log-files by creating the database to automatically archive log files in ARCHIVELOG mode,
which is discussed in detail in the Oracle documentation.
Since redo logs are crucial for restoring a database in the event of a failure, many Oracle shops set up an
instance to keep multiple copies of a redo log file.
Now When I try to practically I take backup of database using RMAN and I do create some table and insert some record so new changes done on after taking backup.
But I want to learn or do practically live how to recover database using redo log file.
so how to simulate it our own laptop?
With RMAN, an easy way would be a recovery to a point in time, eg
1) 9am, take a full backup
2) 9:10am, create some new tables, add rows etc etc
3) use RMAN to recover to 9:05am
4) prove that the new changes are no longer there
Then you've proven that RMAN can recover to a point that is *not* the same as the point in time that the backup was taken.
If you want to do all this manually to understand the process, you can do:
1) alter database begin backup
2) copy all the datafiles somewhere
3) alter database end backup
then do
shutdown abort
copy the backed up copies of the datafiles over the real files
startup mount
recover database until time ...
and you'll be prompted for archive logs etc to be applied..
Lots of good walk throughs in the docs:
http://docs.oracle.com/database/122/BRADV/rman-complete-database-recovery.htm#GUID-D908719C-9D46-4084-850C-0F81C25094EB