Oracle Flashback Technologies (total)

Oracle Flashback Technologies

With the addition of the Flashback query technology in Oracle 9i, the flashback query provides a simple, powerful, and completely non-disruptive mechanism for recovering from human error in the database. With a flashback query, users can view the state of the data at a point in time, without having to make any modifications to the database structure. Oracle 10g extends the flash-back technology, providing a fast and simple recovery mechanism at the database, table, row, and transaction levels, respectively.

The Oracle 10g in-flash technology includes the following technologies:

• Flashback database: Quickly change the database back to a previous point in time without the need for restore and recover operations, reducing the chance of downtime and human error occurrence

• Flashback table: Restores the table to a previous point in time, does not require a restore operation, etc.

• Flashback drop: Restore a table that was mistakenly deleted

• Flash back version query: Use undo Data

• Flashback transaction query: Viewing at the transaction level

Oracle 11g provides a flash-back data archive (Flashback Archive) technology for managing and querying long-term historical data.

If an error occurs, such as when the batch job executes two times, the administrator can perform a flashback to quickly restore the database to a previous state without having to restore the backup and perform a point-in-time recovery. Flash back technology is not just at the database level, but also at the table level.

The following table shows a diagram of the flashback characteristics

Turn on flashback to set up database archiving and setup Flash recovery Area (FRA)

1. Ensure that the database is in archive mode

2. Setting the Flashback Recovery area

#设置闪回区大小:

Sql> alter system set DB_RECOVERY_FILE_DEST_SIZE=6G Scope=both;

#设置闪回区位置

#设置闪回retention目标, measured in minutes

Sql> alter system set db_flashback_retention_target=3600 scope=both sid= ' * ';

3. Turn on the database flash back function

#开启数据库闪回功能

Sql> ALTER DATABASE flashback on;

4. Confirm

How to calculate the size of the fast flash back zone:

Disk Quota =size of a copy of the database +size of an incremental backup +size of (n+1) days of archived redo logs +size of ( y+1) days of foreign archived redo logs (for logical standby) +size of control file +size of an online redo log member * n Umber of log groups +size of flashback logs (based on db_flashback_retention_target value)

Table flashback is not supported for the following types of tables:
• Advanced Team List
• Separate partition table or sub-partition
• Materialized views
• Nested tables
• Object Table
• Remote Tables
• Static data dictionary table
system table
• Part of the cluster table

Oracle Flashback Technologies (total)