How to Enable ArchiveLog Mode in Oracle Database?

 To enable ARCHIVELOG mode in an Oracle Database, follow these steps. ARCHIVELOG mode ensures that Oracle logs all database changes to archived redo logs, enabling point-in-time recovery. This mode is essential for backup and recovery strategies.

Prerequisites:

• You must have SYSDBA privileges.
• Make sure you have a valid backup of your database before changing the mode.

Steps to Enable ARCHIVELOG Mode:

1. Check the Current Mode (Optional): First, verify whether the database is currently in ARCHIVELOG mode or not. Connect to your database using SQL*Plus or any SQL client:

   
   sqlplus / as sysdba
   

   Then, run the following query to check the current mode:

   
   SELECT log_mode FROM v$database;
   

   If it returns NOARCHIVELOG, the database is not in ARCHIVELOG mode.

2. Shut Down the Database: To enable ARCHIVELOG mode, the database needs to be mounted but not open. To do this, shut down the database:

   
   SHUTDOWN IMMEDIATE;
   

   Or if the database is not in a consistent state, you can use:

   
   SHUTDOWN ABORT;
   

3. Start the Database in MOUNT Mode: After shutting down the database, start it in MOUNT mode, which allows you to change the database settings without opening it:

   
   STARTUP MOUNT;
   

4. Enable ARCHIVELOG Mode: Once the database is in MOUNT mode, you can enable ARCHIVELOG mode with the following command:

   
   ALTER DATABASE ARCHIVELOG;
   

5. Check the Status: Verify that the database is now in ARCHIVELOG mode:

   
   SELECT log_mode FROM v$database;
   

   It should return ARCHIVELOG.

6. Open the Database: Now that ARCHIVELOG mode is enabled, you can open the database:

   
   ALTER DATABASE OPEN;
   

7. Configure Archive Log Destination (Optional but Recommended): You may want to specify where to store the archived redo logs. To check the current archive log destination, use the following:

   
   SHOW PARAMETER log_archive_dest;
   

   If needed, you can change the destination using:

   
   ALTER SYSTEM SET LOG_ARCHIVE_DEST='/path/to/archive/destination' SCOPE=BOTH;
   

   Replace /path/to/archive/destination with the appropriate path on your system.

8. Verify Archive Log Process: Ensure that the archive log process is running. Check for any errors in the alert log or use the following query to check the archive log status:

   
   ARCHIVE LOG LIST;
   

   This will show you the current log mode, the archive log destination, and the current log sequence.

Backup the Database After Enabling ARCHIVELOG Mode

It’s recommended to take a full backup of the database after enabling ARCHIVELOG mode because ARCHIVELOG mode will start generating archived redo logs for all transactions, which can be crucial for recovery.