How to recover deleted data in oracle

With the widespread popularity of database applications, data security issues have received more and more attention. However, the problem of data loss or accidental deletion is still inevitable. For this kind of situation, Oracle database provides a variety of data recovery methods. This article will introduce the methods and precautions for recovering deleted data in Oracle.

1. Use flashback technology to recover deleted data

Oracle database provides a technology called flashback (Flashback) that can quickly recover deleted data. This technology uses information in the Oracle database Undo table space to restore deleted data. Before performing flashback, you need to ensure that the database is in archive mode, otherwise this technology cannot be used.

The following are the steps to use flashback technology to recover deleted data:

Step 1: Determine the tables that need to be restored

First, you need to determine the tables that need to be restored and their corresponding recovery time point. You can use the following statement to query the past status of the table:

SELECT * FROM table_name AS OF TIMESTAMP TO_TIMESTAMP('恢复时间点', 'YYYY-MM-DD HH24:MI:SS');

Among them, the recovery time point needs to be adjusted according to the actual situation.

Step 2: Recover the table

Use the following statement to flash back the table at the specified time point:

FLASHBACK TABLE table_name TO TIMESTAMP TO_TIMESTAMP('恢复时间点', 'YYYY-MM-DD HH24:MI:SS');

Step 3: Verify the recovery result

Yes Use the following statement to verify whether the deleted data has been successfully restored:

SELECT * FROM table_name;

2. Use RMAN to restore deleted data

RMAN is a command line tool provided by Oracle that can be used To restore data in the database. If the database is in a backup state, you can use RMAN to restore it.

The following are the steps to use RMAN to recover deleted data:

Step 1: Check the database status

First you need to check the database status:

SELECT STATUS FROM V$INSTANCE;

If the status For OPEN, you need to close the database:

SHUTDOWN IMMEDIATE;

Step 2: Start RMAN

Enter the following command on the command line to start RMAN:

rman target /

Step 3: Connect to the database

Connect to the database that needs to be restored:

CONNECT TARGET

Step 4: Select the time point to be restored

According to the backup recovery point, select the time point to be restored:

RUN {
SET UNTIL TIME 'time_stamp';
RESTORE TABLE table_name;
RECOVER TABLE table_name;
}

The time_stamp needs to be adjusted according to the actual situation.

Step 5: Verify the recovery results

After the recovery is completed, you can use the following statement to verify whether the deleted data has been successfully recovered:

SELECT * FROM table_name;

3. Restore manifest file Function

Oracle provides a function called the manifest file, which can record all information during database backup, including backup date, backup mode, backup type, etc. Use the manifest file function to easily find backups and restore them.

Here are the steps to recover deleted data using the manifest file feature:

Step 1: Back up the manifest file

Use the following command to back up the manifest file:

BACKUP INCREMENTAL LEVEL 0 DATABASE INCLUDE CURRENT CONTROLFILE TAG backup_tag;

The backup_tag can be named according to the actual situation.

Step 2: Find the backup

Find the backup that needs to be restored:

LIST BACKUP TAG backup_tag;

Step 3: Select the backup that needs to be restored

According to the path of the backup file and The backup date determines the backup that needs to be restored:

CATALOG START WITH '备份路径' NOPROMPT;
SELECT * FROM RC_BACKUP_SET WHERE START_TIME = '备份日期';

Step 4: Restore deleted data

Use the following command to restore deleted data:

EXPORT TABLESPACE table_name_1, table_name_2
DATAFILE '数据文件路径' 1;

Among them, table_name_1 and table_name_2 are required The restored table name and data file path need to be adjusted according to the actual situation.

Step 5: Verify the recovery result

You can use the following statement to verify whether the deleted data has been successfully restored:

SELECT * FROM table_name;

It should be noted that before using the above method to restore data When doing so, the integrity of the backup must be ensured. In addition, confirmation is required before recovery to avoid unnecessary losses.

To sum up, Oracle provides a variety of methods to recover deleted data, and you can choose the appropriate method for data recovery according to the actual situation. At the same time, in order to avoid data loss or deletion, it is recommended to back up the database regularly and take corresponding data security measures.

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