Lesson 1

In the previous module, you learned about managing database redo log files. In most environments, as a database administrator (DBA), you will find yourself with the related responsibility of archiving those redo log files. Archiving in this context refers to the process of making an offline copy of every redo log file generated while the database is running. These archived log files are crucial to your ability to recover the database should any data files become damaged.
In this module, you will learn how to perform the following tasks:

1. Place a database in archivelog mode
2. Control the archive log destination
3. Specify the naming convention to use for archive log files
4. Enable automatic archiving of log files
5. Manually archive log files
6. View the log history

In Oracle 11g R2, the DBA can configure the database to archive redo log files by using **ARCHIVELOG mode**. Here’s a step-by-step process to set up and manage redo log file archiving:

Steps to Enable ARCHIVELOG Mode

1. Start the Database in Mount State

   • SHUTDOWN IMMEDIATE;
     STARTUP MOUNT;
             

   • The database needs to be in the MOUNT state to enable ARCHIVELOG mode.
2. Enable ARCHIVELOG Mode

   • ALTER DATABASE ARCHIVELOG;
             

3. Open the Database

   • ALTER DATABASE OPEN;
             

Configure the Archive Destination

• By default, the archive log files are stored in a specified directory. You can set the location using the LOG_ARCHIVE_DEST parameter.

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

• You may also use LOG_ARCHIVE_DEST_n for multiple archive destinations if needed.

Verify the ARCHIVELOG Mode

To confirm that the database is in ARCHIVELOG mode, run:

ARCHIVE LOG LIST;
        

Managing the Archived Redo Logs

1. Manually Archiving Redo Logs
   • If you want to archive a redo log manually, you can use:

     ALTER SYSTEM ARCHIVE LOG CURRENT;
             

2. Monitoring Archive Log Usage
   • You can query the V$ARCHIVED_LOG view to monitor and manage the archived redo logs:

     SELECT SEQUENCE#, FIRST_TIME, NEXT_TIME, ARCHIVED
     FROM V$ARCHIVED_LOG;
             

3. Housekeeping
   • It is crucial to manage the storage space for archived logs to prevent the disk from filling up.
   • Implement a backup and deletion strategy for archived logs using RMAN (Recovery Manager) or scripts.

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Important Notes

• Archiving Process: When the database is in ARCHIVELOG mode, the archiver (ARCn) process automatically copies redo log files to the specified archive destination whenever a log switch occurs.
• Performance Impact: Ensure that the archive destination has enough space and is appropriately managed to avoid performance issues related to log archiving.

In the next lesson, you will learn how to place a database into archivelog mode.