Introduction
Need to enable archive log mode in Oracle 19c but unsure of the exact steps? Converting from NOARCHIVELOG to ARCHIVELOG mode is essential for production databases, yet many DBAs hesitate due to concerns about downtime and configuration complexity.
In this guide, I’ll walk through the complete process of enabling archive log mode in Oracle 19c with real commands and outputs from an actual implementation. Whether you’re preparing for Data Guard setup, enabling point-in-time recovery, or meeting compliance requirements, this step-by-step approach will get you there safely.
Quick Reference: Enable Archive Log Mode Commands
For experienced DBAs who need the commands quickly
-- 1. Shutdown
SHUTDOWN IMMEDIATE;
-- 2. Mount
STARTUP MOUNT;
-- 3. Enable archivelog
ALTER DATABASE ARCHIVELOG;
-- 4. Set destination (ASM example)
ALTER SYSTEM SET log_archive_dest_1='LOCATION=+ARCH' SCOPE=BOTH;
-- 5. Open
ALTER DATABASE OPEN;
-- 6. Verify
SELECT log_mode FROM v$database;Continue reading for detailed explanation and troubleshooting.
Why Use ARCHIVELOG Mode?
Before diving into the implementation, it’s important to understand why ARCHIVELOG mode matters:
- Point-in-time recovery: Recover your database to any point in time, not just to the most recent backup
- Online backups: Take backups while the database is open and operational
- Data Guard configuration: Required for setting up standby databases
- Flashback Database feature: Enables Oracle’s flashback technology
According to the Oracle Database Backup and Recovery User’s Guide, properly configured ARCHIVELOG mode can reduce recovery time objectives (RTOs) by up to 80% compared to NOARCHIVELOG databases.
Current Configuration Check
First, let’s check the current log mode of our database:
SQL> SELECT log_mode FROM v$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$database;
LOG_MODE
------------
ARCHIVELOG
Post-Configuration Considerations
After enabling ARCHIVELOG mode, consider these important follow-up tasks:
- Monitor archive log generation: Ensure you have sufficient space in your archive destination using Oracle Enterprise Manager
- Implement a log management strategy: Set up automated archivelog backups and deletion through RMAN
- Review RMAN backup strategy: Update your backup scripts to take advantage of ARCHIVELOG capabilities
- Test recovery scenarios: Validate that you can perform point-in-time recovery
For more guidance on optimizing your backup strategy, refer to our previous post on Optimizing RMAN Backup Performance in Oracle 19c.
Common Issues and Troubleshooting
When setting up ARCHIVELOG mode, you might encounter these common issues:
- Insufficient disk space: Ensure your archive destination has adequate storage
- Permission problems: The Oracle user must have write access to the archive destination
- Performance impact: Monitor database performance closely after enabling ARCHIVELOG mode
For detailed troubleshooting, check out the Official Oracle Database Administrator’s Guide.
Frequently Asked Questions
Can I enable archive log mode without downtime?
No, enabling ARCHIVELOG mode requires a database restart. The database must be in MOUNT state to execute ALTER DATABASE ARCHIVELOG.
How much disk space do archive logs need?
Plan for 2-3x your daily redo generation.
Monitor with: SELECT SUM(BLOCKS * BLOCK_SIZE)/1024/1024 MB_PER_DAY FROM V$ARCHIVED_LOG WHERE COMPLETION_TIME > SYSDATE-1;
What happens if archive destination fills up?
Database operations will hang until space is available. Always configure RMAN to delete obsolete archivelogs automatically.
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!