Manually clear backup data

You can manually clear backup data as needed.

You can run the ALTER SYSTEM command to delete the specified backup_set_id, backup_piece_id, and backup_round_id, or clear expired data.

Preparations

Before you manually clear the expired backup data, you must specify the expiration time and clearing policy of backup data by setting recovery_window and auto_delete_obsolete_backup in the backup_dest_option configuration item.

Example:

obclient> ALTER SYSTEM SET backup_dest_option='log_archive_checkpoint_interval=5s&recovery_window=7d&auto_delete_obsolete_backup=false&log_archive_piece_switch_interval=120s&backup_copies=2';

In the example:

• log_archive_checkpoint_interval specifies the interval for log backup.

  If you do not specify this parameter in the backup_dest_option configuration item, the value of the cluster-level configuration item log_archive_checkpoint_interval is used by default. If you do not specify either backup_dest_option or log_archive_checkpoint_interval, the default value 120s is used. We recommend that you use backup_dest_option to specify the interval for log backup.

• recovery_window specifies the retention period of backup data.

  If you do not specify this parameter in the backup_dest_option configuration item, the value of the cluster-level configuration item backup_recovery_window is used by default. If you do not specify either backup_dest_option or backup_recovery_window, the default value 0 is used, indicating that backup data will never expire. We recommend that you use backup_dest_option to specify the retention period of backup data.

  When the backup expires, you can manually clear it.

• auto_delete_obsolete_backup specifies whether to automatically delete expired backup data.

  If you do not specify this parameter in the backup_dest_option configuration item, the value of the cluster-level configuration item auto_delete_expired_backup is used by default. If you do not specify either backup_dest_option or auto_delete_expired_backup, the default value false is used, indicating that expired backup data will not be automatically deleted. In this case, auto_delete_obsolete_backup must be set to false. We recommend that you use backup_dest_option to specify whether to automatically clear expired backup data.

• log_archive_piece_switch_interval specifies whether to automatically split the content of the log file directory into multiple directories based on a specific interval. The default value is 0, indicating that no splitting is performed. The valid value range is [1d,7d].

• backup_copies specifies how many copies of backup data must be retained for backup redundancy. The default value is 1. If you have specified backup_backup_dest, we recommend that you set backup_copies to 2. The valid value range of backup_copies is [1,8].

  If you set backup_copies to 1, the system deletes backup data without considering whether its secondary backup is successful. If you set backup_copies to 2, the system will only automatically delete backup data in backup_dest after its secondary backup has been saved to backup_backup_dest.

For more information about backup_dest_option, see the "backup_dest_option" topic in Reference Guide (MySQL Mode) or Reference Guide (Oracle Mode).

Clear specified backups

1. Log on to the database as the root user of the sys tenant.

2. Query the CDB_OB_BACKUP_SET_DETAILS and CDB_OB_BACKUP_PIECE_FILES views to find the backup_set_id, piece_id, and round_id corresponding to the backup data to be cleared.

   For more information about the fields in CDB_OB_BACKUP_SET_DETAILS and CDB_OB_BACKUP_PIECE_FILES, see the "oceanbase.CDB_OB_BACKUP_SET_DETAILS" and "oceanbase.CDB_OB_BACKUP_PIECE_FILES" topics in Reference Guide (MySQL Mode).

3. Select the command that is appropriate for your need to clear the backup data.

   • Clear backups with the specified backup_set_id

     obclient> ALTER SYSTEM DELETE BACKUPSET backup_set_id;
     

     For example, you can run the following command to delete the backup whose backup_set_id is 1:

     obclient> ALTER SYSTEM DELETE BACKUPSET 1;
     

     When you run the DELETE BACKUPSET command to clear the backups, the following constraints apply:

     • If the backup_dest of the backup_set_id to be deleted is the same as the destination specified in the backup_dest configuration item, at least one complete and valid backup copy is retained. Otherwise, the constraint of retaining one valid backup copy does not apply.

     • If the backup_dest of the backup_set_id to be deleted is the same as the destination specified in the backup_dest configuration item, the backup sets must be deleted in a specific order. For example, backup sets with backup_set_id of 1, 2, and 3 must be deleted in the order of 1 first, followed by 2, and 3 last. Otherwise, the constraint on the deletion order of backup sets does not apply.

     • The command fails if the specified backup_set_id does not exist, or the backup of the specified backup_set_id is still ongoing.

   • Clear backups with the specified piece_id

     obclient> ALTER SYSTEM DELETE BACKUPPIECE piece_id;
     

     When you run the DELETE BACKUPPIECE command to clear the backups, the following constraints apply:

     • You can only delete backup pieces in the Frozen or Inactive status.

     • If the backup_dest of the piece_id to be deleted is the same as the destination specified in the backup_dest configuration item, and the existing backups do not fully cover the backup piece, the corresponding piece_id cannot be deleted. Otherwise, the corresponding piece_id can be deleted regardless of whether the existing backups fully cover the backup piece.

     • If the backup_dest of the piece_id to be deleted is the same as the destination specified in the backup_dest configuration item, the backup pieces must be deleted in a specific order to prevent log discontinuity. For example, backup pieces with piece_id of 1, 2, and 3 must be deleted in the order of 1 first, followed by 2, and 3 last. Otherwise, the constraint on the deletion order of backup pieces does not apply.

   • Clear all data in a log backup round with the specified round_id

     obclient> ALTER SYSTEM DELETE BACKUPROUND round_id;
     

     The constraints on the DELETE BACKUPPIECE command also apply on the DELETE BACKUPROUND command:

     • You can only delete backup rounds in the Stop status.

     • If the backup_dest of the round_id to be deleted is the same as the destination specified in the backup_dest configuration item, and the existing backups do not fully cover the backup round, the corresponding round_id cannot be deleted. Otherwise, the corresponding round_id can be deleted regardless of whether the existing backups fully cover the backup round.

     • If the backup_dest of the round_id to be deleted is the same as the destination specified in the backup_dest configuration item, the backup rounds must be deleted in a specific order to prevent log discontinuity. For example, backup rounds with round_id of 1, 2, and 3 must be deleted in the order of 1 first, followed by 2, and 3 last. Otherwise, the constraint on the deletion order of backup rounds does not apply.

Clear expired backups

1. Log on to the database as the root user of the sys tenant.

2. Run the following command to clear expired backups:

   obclient> ALTER SYSTEM DELETE OBSOLETE;
   

   The DELETE OBSOLETE command has the following constraints:

   • If no or only one valid backup set exists, the data of archived logs cannot be cleared if it is split into multiple backup pieces.

   • The DELETE OBSOLETE command only deletes expired backups whose storage path is the same as the destination specified in backup_dest. For more information about expired backups whose destination is changed, see "Clear specified backups" in this topic.

   • The DELETE OBSOLETE command does not delete secondary backups.

   • The command fails if the number of existing backup copies is smaller than the value specified for backup_copies in backup_dest_option.