Introduction
ARCHIVELOG mode is a critical configuration for any production Oracle database that requires point-in-time recovery capabilities. In this comprehensive guide, I’ll walk through the process of converting an Oracle 19c database from NOARCHIVELOG to ARCHIVELOG mode, with commands and outputs from a real-world implementation.
Why Use ARCHIVELOG Mode?
Before diving into the implementation, it’s important to understand why ARCHIVELOG mode matters:
- Point-in-time recovery: Recover your database to any point in time, not just to the most recent backup
- Online backups: Take backups while the database is open and operational
- Data Guard configuration: Required for setting up standby databases
- Flashback Database feature: Enables Oracle’s flashback technology
According to the Oracle Database Backup and Recovery User’s Guide, properly configured ARCHIVELOG mode can reduce recovery time objectives (RTOs) by up to 80% compared to NOARCHIVELOG databases.
Current Configuration Check
First, let’s check the current log mode of our database:
SQL> SELECT log_mode FROM v$database;
LOG_MODE
------------
NOARCHIVELOG
As we can see, our database is currently in NOARCHIVELOG mode, which means we cannot perform point-in-time recovery.
Step-by-Step Implementation
1. Shut Down the Database
To switch to ARCHIVELOG mode, we first need to shut down the database gracefully:
SQL> SHUTDOWN IMMEDIATE;
Database closed.
Database dismounted.
ORACLE instance shut down.
2. Start the Database in Mount State
Next, we start the instance but only mount the database (not open it):
SQL> STARTUP MOUNT;
ORACLE instance started.
Total System Global Area 9965662984 bytes
Fixed Size 9188104 bytes
Variable Size 1778384896 bytes
Database Buffers 8153726976 bytes
Redo Buffers 24363008 bytes
Database mounted.
3. Enable ARCHIVELOG Mode
While the database is in MOUNT state, we can enable ARCHIVELOG mode:
SQL> ALTER DATABASE ARCHIVELOG;
Database altered.
4. Configure Archive Log Destination
Before opening the database, we set up the destination for archive logs. In our case, we’re using Oracle ASM (+ARCH):
SQL> ALTER SYSTEM SET log_archive_dest_1='LOCATION=+ARCH' SCOPE=BOTH;
System altered.
The SCOPE=BOTH parameter ensures this setting is applied both immediately and persists across database restarts.
5. Open the Database
With our configuration in place, we can now open the database:
SQL> ALTER DATABASE OPEN;
Database altered.
6. Verify the Configuration
Finally, we verify our archive log destination settings:
SQL> SHOW PARAMETER log_archive_dest;
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
log_archive_dest string
log_archive_dest_1 string LOCATION=+ARCH
log_archive_dest_10 string
[...]
You should also verify the database is now in ARCHIVELOG mode:
SQL> SELECT log_mode FROM v$database;
LOG_MODE
------------
ARCHIVELOG
Post-Configuration Considerations
After enabling ARCHIVELOG mode, consider these important follow-up tasks:
- Monitor archive log generation: Ensure you have sufficient space in your archive destination using Oracle Enterprise Manager
- Implement a log management strategy: Set up automated archivelog backups and deletion through RMAN
- Review RMAN backup strategy: Update your backup scripts to take advantage of ARCHIVELOG capabilities
- Test recovery scenarios: Validate that you can perform point-in-time recovery
For more guidance on optimizing your backup strategy, refer to our previous post on Optimizing RMAN Backup Performance in Oracle 19c.
Common Issues and Troubleshooting
When setting up ARCHIVELOG mode, you might encounter these common issues:
- Insufficient disk space: Ensure your archive destination has adequate storage
- Permission problems: The Oracle user must have write access to the archive destination
- Performance impact: Monitor database performance closely after enabling ARCHIVELOG mode
For detailed troubleshooting, check out the Official Oracle Database Administrator’s Guide.
Conclusion
Enabling ARCHIVELOG mode is a fundamental step in preparing your Oracle database for proper backup and recovery operations. While it introduces additional storage and management requirements, the benefits in terms of recoverability and reduced downtime risk far outweigh these considerations for most production environments.
Remember that the specific example shown here is for an Oracle 19c database (version 19.25.0.0.0), but the process is similar across most Oracle database versions.
Related Articles
- Understanding Oracle Backup and Recovery Strategies
- Configuring Automatic Storage Management (ASM) in Oracle 19c
- Oracle Data Guard Configuration Guide
Have you recently switched your database to ARCHIVELOG mode? Share your experience in the comments below!