In Oracle databases, Flashback logs are used to restore the database to a previous point in time. They are stored in the Fast Recovery Area (FRA) and can grow over time, leading to space issues. Here’s how to check and delete Flashback logs in Oracle:

1. Check Flashback Logs

To check the amount of space used by Flashback logs and other files in the Fast Recovery Area (FRA), you can query the V$FLASH_RECOVERY_AREA_USAGE view:

SELECT FILE_TYPE, PERCENT_SPACE_USED, PERCENT_SPACE_RECLAIMABLE, NUMBER_OF_FILES
FROM V$FLASH_RECOVERY_AREA_USAGE;

This will show the space used by Flashback logs, archivelogs, backups, and other FRA components.

You can also check the total size of the FRA and how much space is used by querying the V$RECOVERY_FILE_DEST view:

SELECT NAME, SPACE_LIMIT, SPACE_USED, SPACE_RECLAIMABLE, NUMBER_OF_FILES
FROM V$RECOVERY_FILE_DEST;

2. Delete Flashback Logs

Flashback logs cannot be manually deleted directly because Oracle manages them internally. However, you can manage space by:

A. Adjusting Flashback Retention Target

Oracle retains Flashback logs based on the DB_FLASHBACK_RETENTION_TARGET parameter, which specifies the amount of time (in minutes) that the logs are kept. You can lower this value if you want to reduce the size of Flashback logs:

ALTER SYSTEM SET DB_FLASHBACK_RETENTION_TARGET = 60; -- Set retention to 60 minutes

B. Purging Flashback Logs Automatically

If the FRA runs out of space, Oracle automatically reclaims space by deleting old Flashback logs. You can ensure this process by monitoring and managing the FRA size:

ALTER SYSTEM SET DB_RECOVERY_FILE_DEST_SIZE = 10G; -- Set FRA size to 10GB

If Flashback logs are occupying too much space, Oracle will delete the oldest logs first to free up space.

C. Turning Off Flashback Logging

You can also disable Flashback logging if you no longer need it. Be cautious with this, as it will remove all existing Flashback logs and you won’t be able to flashback the database anymore:

ALTER DATABASE FLASHBACK OFF;

To turn it back on:

ALTER DATABASE FLASHBACK ON;

D. Manually Removing Files from FRA (Not Recommended)

Manually deleting files from the operating system level in the FRA is not recommended because Oracle manages these files. However, in extreme cases, you might delete obsolete backups and archive logs using RMAN:

RMAN> DELETE OBSOLETE;

Or delete archivelogs:

RMAN> DELETE ARCHIVELOG ALL;

These steps will free up space, allowing Oracle to manage Flashback logs more effectively.