How Do I Fix Ora 00257?

The ORA-00257 error, "Archiver error. Connect internal only, until freed," indicates that the Oracle database's archiver process (ARCn) cannot write archived redo log files to one or more configured archive destinations. This is most commonly due to a lack of disk space on the target mount point, but can also be caused by incorrect permissions, inaccessible network locations, or an overloaded I/O subsystem. When this error occurs, the database will eventually halt all activity that generates redo, preventing new transactions until the issue is resolved.

Understanding the `ORA-00257` Error

Oracle databases operate in ARCHIVELOG mode to enable point-in-time recovery and ensure data durability. Redo logs record all changes made to the database. Once a redo log file is full, it is archived (copied) to a designated location before it can be reused by the database. The ORA-00257 error means this archiving process has failed, causing the database to pause its operations to prevent data loss or corruption.

Immediate Steps to Resolve `ORA-00257`

Resolving ORA-00257 primarily involves freeing up space in the archive log destination or redirecting the archive logs to an available location. Here are the practical solutions:

1. Add More Space to the Archive Log Mount Point

This is the most common and often the simplest solution. The ORA-00257 error frequently arises because the disk partition or mount point where archive logs are written has run out of space.

Identify the Destination: Check the LOG_ARCHIVE_DEST_n parameters to find out where your archive logs are being written. You can query V$ARCHIVE_DEST or V$ARCHIVE_DEST_STATUS for details.
```
SELECT DEST_ID, STATUS, DESTINATION FROM V$ARCHIVE_DEST_STATUS WHERE STATUS != 'INACTIVE';
```
Check Disk Usage: Use operating system commands (e.g., df -h on Linux/Unix, Get-Volume on PowerShell for Windows) to check the available space on the identified mount point.
Extend Storage: If space is insufficient, work with your system administrator to extend the disk partition or add more storage to the mount point.

2. Backup and Delete Archive Logs Using RMAN

Oracle's Recovery Manager (RMAN) is the recommended tool for managing backups and archive logs. Backing up archive logs and then deleting them is an efficient way to free up space while maintaining recoverability.

Connect to RMAN:
```
rman target /
```
Backup Archive Logs and Delete Input: Execute a command to back up the archive logs to a different location (e.g., tape or another disk) and then delete the originals from the source destination.
```
BACKUP ARCHIVELOG ALL DELETE INPUT;
```
This command backs up all non-backed-up archive logs and then deletes them after a successful backup. You can also specify a time window:
```
BACKUP ARCHIVELOG FROM TIME 'SYSDATE - 7' DELETE INPUT;
```
For specific log sequences:
```
BACKUP ARCHIVELOG FROM SEQUENCE 100 TO SEQUENCE 200 DELETE INPUT;
```
Always verify that your backups are successful and accessible before relying solely on them.

3. Temporarily Move the Archive Log Location

If extending space or backing up immediately isn't feasible, you can temporarily redirect archive logs to another mount or drive that has sufficient space.

Identify an Alternate Location: Find a mount point or directory with ample free space.
Alter Archive Destination: Connect to the database as a SYSDBA user and change the LOG_ARCHIVE_DEST_1 (or relevant destination) parameter.
```
ALTER SYSTEM SET LOG_ARCHIVE_DEST_1='LOCATION=/new/temporary/archive/path' SCOPE=BOTH;
```
This command updates the parameter for both the current instance and the server parameter file (SPFILE). If your database is a Real Application Clusters (RAC) environment, ensure the path is accessible to all instances or adjust for individual instances.
Clear the Error: After changing the destination, the database should automatically resume archiving. If it doesn't, you might need to issue an ALTER SYSTEM ARCHIVE LOG ALL; command to force a log switch and clear the backlog, or a SHUTDOWN IMMEDIATE; followed by STARTUP; if the error persists.

4. Delete Archive Logs Without Backup (Use with Caution)

If data recoverability is not critical for the specific range of deleted archive logs (e.g., if you have recent full backups and don't require point-in-time recovery past that backup point), you can delete archive logs directly. This option should only be considered as a last resort and with a clear understanding of the risks involved, as it impacts your ability to perform point-in-time recovery.

Using RMAN (Recommended for Deletion):
```
rman target /
DELETE ARCHIVELOG ALL;
```
This command deletes all archive logs recorded in the RMAN repository. You can specify a time window or sequence range if needed.
```
DELETE ARCHIVELOG UNTIL TIME 'SYSDATE - 1';
```
Using Operating System Commands (Discouraged): You can manually delete files from the archive log destination using rm (Linux/Unix) or del (Windows). However, doing this without RMAN means the control file still believes those logs exist, which can cause issues during recovery operations. If you delete files manually, you must also catalog the changes with RMAN:
```
rman target /
CROSSCHECK ARCHIVELOG ALL;
DELETE EXPIRED ARCHIVELOG ALL;
```
This updates RMAN's catalog to reflect the deleted files.

Post-Resolution Steps

After implementing a fix, always perform the following:

Verify Archiving Resumes: Check V$ARCHIVE_DEST_STATUS again to ensure the archiving status is VALID and ACTIVE.
Monitor Disk Space: Implement proactive monitoring for the archive log destination to prevent recurrence.
Review Retention Policy: Adjust your RMAN retention policy for archive logs (CONFIGURE ARCHIVELOG DELETION POLICY TO BACKED UP N TIMES TO DISK; or TO APPLIED ON STANDBY;) to automatically manage space.

Preventing Future `ORA-00257` Errors

Proactive measures are key to avoiding this critical error:

Disk Space Monitoring: Implement alerts for low disk space on all archive log destinations.
RMAN Backup Schedule: Ensure a robust RMAN backup strategy is in place, including regular archive log backups with DELETE INPUT to manage space.
Flash Recovery Area (FRA): Utilize the Flash Recovery Area (FRA) for managing backups and archive logs. Configure DB_RECOVERY_FILE_DEST and DB_RECOVERY_FILE_DEST_SIZE parameters, allowing Oracle to automatically manage space within the FRA based on retention policies.
Archive Log Destination Sizing: Properly size your archive log destinations based on transaction volume and RMAN retention policies.
Multiple Destinations: Configure multiple archive log destinations for redundancy, especially to a standby database for disaster recovery.

By understanding the cause and implementing these solutions and preventive measures, you can effectively manage and resolve ORA-00257 errors.