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Implementing Oracle Flashback Technology for Point-in-Time Recovery

Learn how Oracle Flashback Technology enables point-in-time recovery, undoing mistakes and recovering lost data efficiently without full backups or downtime

oracle configurationintermediate

by OracleDba

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Flashback Query

- Retrieve past data from a table using a simple SQL query. - Example: This retrieves the state of the employees table at a specific time.

Code/Command (click line numbers to comment):

SELECT * FROM employees AS OF TIMESTAMP TO_TIMESTAMP('2024-12-20 10:00:00', 'YYYY-MM-DD HH24:MI:SS');

Flashback Table

- Undo DML changes to one or more tables to a previous timestamp. - Example:

Code/Command (click line numbers to comment):

FLASHBACK TABLE employees TO TIMESTAMP TO_TIMESTAMP('2024-12-20 10:00:00', 'YYYY-MM-DD HH24:MI:SS');

Flashback Database

- Rewind the entire database to a previous point-in-time without restoring backups.

Flashback Drop

- Recover dropped tables from the Recycle Bin. - Example:

Code/Command (click line numbers to comment):

FLASHBACK TABLE employees TO BEFORE DROP;

Flashback Versions Query

- Retrieve changes made to a row over a time period. To enable Flashback Database, follow these steps:

1. Enable ARCHIVELOG Mode:

Code/Command (click line numbers to comment):

SQL> SHUTDOWN IMMEDIATE;
SQL> STARTUP MOUNT;
SQL> ALTER DATABASE ARCHIVELOG;
SQL> ALTER DATABASE OPEN;

2. Enable Flashback:

Code/Command (click line numbers to comment):

SQL> ALTER DATABASE FLASHBACK ON;

3. Configure the Flash Recovery Area (FRA):

Here’s how you can use Flashback Database for point-in-time recovery:

Code/Command (click line numbers to comment):

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ALTER SYSTEM SET DB_RECOVERY_FILE_DEST='/u01/app/oracle/flash_recovery_area';
ALTER SYSTEM SET DB_RECOVERY_FILE_DEST_SIZE=10G;

1. Identify the SCN or Timestamp:

Use the alert log or queries to find the SCN or timestamp to which you want to flash back.

2. Mount the Database:

Code/Command (click line numbers to comment):

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SHUTDOWN IMMEDIATE;
STARTUP MOUNT;

3. Flashback the Database:

Code/Command (click line numbers to comment):

FLASHBACK DATABASE TO TIMESTAMP TO_TIMESTAMP('2024-12-20 10:00:00', 'YYYY-MM-DD HH24:MI:SS');

4. Open the Database with RESETLOGS:

Imagine you’re working for a multinational company managing a sales database. A junior DBA accidentally drops the customer_orders table. Instead of restoring a full backup and incurring downtime, you: 1. Query the Recycle Bin: 2. Recover the Table: In minutes, the table is back, and you’ve saved hours of work and avoided potential revenue loss. - Monitor FRA Space : Always keep an eye on the Flash Recovery Area to ensure it doesn’t fill up, causing Flashback logs to be overwritten. - Practice on a Test Environment : Familiarize yourself with Flashback commands in a non-production setup. - Combine with RMAN : While Flashback is powerful, always have RMAN backups as a fallback for physical corruptions or media failures.

Code/Command (click line numbers to comment):

ALTER DATABASE OPEN RESETLOGS;

SELECT object_name, original_name FROM recyclebin;

FLASHBACK TABLE customer_orders TO BEFORE DROP;

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