How Do I Disable Archive Log?

To disable archive logging in an Oracle database, you must transition the database from ARCHIVELOG mode to NOARCHIVELOG mode. This process involves specific SQL commands executed while the database is in a mounted state, and it temporarily requires database downtime.

Understanding Archive Log Modes

Oracle databases operate in one of two logging modes: ARCHIVELOG or NOARCHIVELOG. The choice significantly impacts your database's recovery capabilities.

ARCHIVELOG Mode: In this mode, Oracle actively saves copies of filled redo log files, known as archive logs. These logs are vital for point-in-time recovery, allowing you to restore your database to any specific moment in time. This mode is essential for disaster recovery, high availability solutions like Oracle Data Guard, and ensuring minimal data loss in production environments.
NOARCHIVELOG Mode: When operating in NOARCHIVELOG mode, Oracle does not retain copies of filled redo log files. While this can reduce disk space requirements and slightly simplify administration for non-critical development or test databases, it prevents point-in-time recovery from backups. In this mode, you can only recover the database to the exact state of the last full backup, meaning any transactions processed since that backup will be permanently lost if a failure occurs.

Step-by-Step Guide to Disabling Archive Log Mode

Disabling archive logging requires a brief period of database downtime as the database needs to be shut down and restarted in a specific mode to alter this fundamental setting.

Prerequisites

Before proceeding, ensure you meet the following requirements:

Operating System Access: You need access to the database server as the operating system user oracle.
SYSDBA Privileges: You must have SYSDBA privileges for the Oracle database.
ORACLE_SID: Know the ORACLE_SID (System Identifier) for your target database.
Full Backup: It is highly recommended to take a full backup of your database before making this change. Switching to NOARCHIVELOG mode impacts your recovery options, and a pre-change backup provides a safe rollback point.

Procedure to Switch to NOARCHIVELOG Mode

Follow these steps carefully to transition your Oracle database to NOARCHIVELOG mode:

Log In to the Operating System:
Access the database server using an SSH client or directly, logging in as the operating system user oracle.
Set Environment Variables:
Set the ORACLE_SID environment variable to point to your specific database. This ensures you are connecting to the correct instance.
```
$ export ORACLE_SID=<MYDB_SID>
```
Replace <MYDB_SID> with the actual System Identifier of your Oracle database (e.g., ORCL, PROD).
Connect to SQL*Plus:
Connect to SQL*Plus as a user with SYSDBA administrative privileges.
```
$ sqlplus / as sysdba
```
Shut Down the Database:
Perform a clean shutdown of the database. This ensures all pending transactions are committed and data files are in a consistent state.
```
SQL> SHUTDOWN IMMEDIATE;
```
Start Up the Database in Mount Mode:
Start the database instance, but only mount it. The database must not be open when you change the archive log mode.
```
SQL> STARTUP MOUNT;
```
Change to NOARCHIVELOG Mode:
Execute the SQL command to switch the database to NOARCHIVELOG mode.
```
SQL> ALTER DATABASE NOARCHIVELOG;
```
This command instructs Oracle to stop generating and retaining archive logs.
Open the Database:
Once the archive log mode is successfully changed, you can open the database for normal operations.
```
SQL> ALTER DATABASE OPEN;
```

Verifying the Change

After following the procedure, it's crucial to confirm that the database is now operating in NOARCHIVELOG mode.
Connect to SQL*Plus as SYSDBA and execute the following query:

SQL> SELECT LOG_MODE FROM V$DATABASE;

The output of this query should display NOARCHIVELOG, confirming the change.

Important Considerations and Risks

While disabling archive logs might appear to simplify database management by reducing disk space and administrative overhead, it introduces significant risks to data recovery and overall data integrity. It is generally not recommended for production environments or any database where data loss is unacceptable.

No Point-in-Time Recovery: The most critical consequence is the loss of point-in-time recovery capabilities. In case of media failure or logical corruption, you can only restore your database to the state of the last full backup. Any data changes or transactions that occurred since that backup will be permanently lost.
Limited Backup Strategies: Hot (online) backups, which allow you to back up the database while it's running, are not possible in NOARCHIVELOG mode. All backups must be performed offline (cold backups) when the database is completely shut down.
No High Availability Features: Features like Oracle Data Guard, which rely on the continuous application of archive logs for replication and standby databases, cannot function in NOARCHIVELOG mode.
Reduced Disaster Recovery Capabilities: Your ability to recover from various failure scenarios, including disk failures, human error, or database corruption, is severely limited.

For more detailed information on managing archive log mode, refer to the Oracle Database ARCHIVELOG Mode Documentation. For details on database startup and shutdown, consult the Oracle Database Startup and Shutdown Documentation.

ARCHIVELOG vs. NOARCHIVELOG Mode Summary

This table provides a concise comparison of the two logging modes:

Feature	ARCHIVELOG Mode	NOARCHIVELOG Mode
Recovery Capability	Point-in-time recovery, complete recovery	Only full recovery to the last backup
Data Loss Potential	Minimal (recoverable to almost any point)	Significant (data lost since last full backup)
Backup Type	Online (hot) and offline (cold) backups possible	Only offline (cold) backups
Disk Space	Requires space for archive logs	Less disk space needed (no archive logs)
Complexity	Slightly more complex (managing archive logs)	Simpler administration, but higher risk
Data Guard/Standby	Supported	Not supported
Recommended For	Production, critical development, mission-critical	Non-critical test/development (with high risk tolerance)

Disabling archive logging can simplify certain aspects of database management, but it significantly compromises your database's recovery capabilities and increases the risk of data loss. Always weigh the operational simplicity against the potential for irreparable data loss.