How to recover deleted data using Flashback features in oracle
In Oracle, you can recover deleted data using the Flashback technology if it has been enabled and configured in your database. Flashback technology provides several features for viewing and recovering past states of data, including the ability to recover deleted data without having to perform a complete database restore.
Here's how you can recover deleted data using Flashback features:
1. Check Flashback Feature: Verify that the Flashback feature is enabled in your Oracle database. You can do this by querying the `V$DATABASE` view or by checking the database initialization parameters.
2. Identify the Time Frame: Determine the time frame within which the data was deleted. You will need to specify this time frame when performing the flashback operation.
3.Select a Flashback Method:
- Flashback Query: If the deletion was recent and you want to view the deleted data without permanently recovering it, you can use the `FLASHBACK QUERY` feature to query the state of the data at a specific point in the past.
- Flashback Table: If you want to permanently recover the deleted data, you can use the `FLASHBACK TABLE` feature to restore the contents of a table to a previous state. This operation requires that the table still exists and that Flashback features are enabled.
4. Perform Flashback Operation:
- Using Flashback Query:
SELECT * FROM table_name AS OF TIMESTAMP TO_TIMESTAMP('YYYY-MM-DD HH24:MI:SS', 'YYYY-MM-DD HH24:MI:SS');
Replace `table_name` with the name of the table from which data was deleted, and specify the timestamp (`YYYY-MM-DD HH24:MI:SS`) corresponding to the time when the data was present.
- Using Flashback Table:
FLASHBACK TABLE table_name TO TIMESTAMP TO_TIMESTAMP('YYYY-MM-DD HH24:MI:SS', 'YYYY-MM-DD HH24:MI:SS');
Replace `table_name` with the name of the table from which data was deleted, and specify the timestamp (`YYYY-MM-DD HH24:MI:SS`) corresponding to the time when the data was present.
5. Verify: After executing the flashback operation, verify that the deleted data has been recovered successfully.
It's important to note that the ability to recover deleted data using Flashback features is subject to certain limitations, such as the retention period configured for Flashback operations and the availability of undo data. Additionally, Flashback features may have performance implications, especially for large datasets, so use them judiciously.