In this tutorial we will learn what is redo log files,why we are creating multiple redolog files for Oracle database ,different status of redo log file,purpose of redo log file
What is redo log file in oracle
REDO log file is very essential file for Oracle database which is stored in physical filesystem of hard disk. Normally it is a file which records all changes made in oracle database .
Suppose a user modified any row using SQL query ,the changed data will be stored in redo Buffer in SGA components. Then LGWR process transferred all data from redo Buffer to redo log file under the following conditions.
1. Redo Buffer one third full
2. Every 3 seconds
3. After a successful transaction committed
4. Before data blocks transfer from db buffer cache to data files.
Why we are creating multiple redolog files for Oracle database
It is recommended to create multiple redolog files in oracle database. If there is one redo log file and by accidentally it is corrupted then oracle database is not working properly. So multiples redo files should be created in the oracle database.
Also we should create redo log files on the separated disk. If we have redo log files on single disk and this disk is corrupted for that we lost all redo log files and database will be not worked. Therefore we should create redo log files on separate disk.
Redo log files are very essential file to recover oracle database in case oracle instance crashes by any reason. Now in oracle database many redo log files are created a group.
Redo group is very important while archiving redo log files.suppose group 2 is current that means oracle uses these redo log files which present in group 2 and archive process then archiving redo log files from other group.for that reason database performance is not degraded.
Different status of redo log file
There are three status of redo log files.
1. Current: oracle database uses this redo files to store the online changes data.
2. Active: These files are required to recover oracle database.
3. Inactive:These files are no longer required to recover oracle database.
Purpose of redo log file
In case oracle instance crashes then Redo log files are required to recover oracle database.
In this tutorial we have learned
1. what is redo log files
2. Why we are creating multiple redolog files for Oracle database
3. Different status of redo log file
4. Purpose of redo log file
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