This document discusses Oracle Database's flashback features, which allow users to view or recover past data and metadata. It describes flashback query, version query, transaction query, flashback transaction, flashback data archive, flashback table, flashback drop, and flashback database. These features require privileges like FLASHBACK and supplemental redo logging. They enable point-in-time data recovery without needing to restore backups. The document provides examples and best practices for configuring and using Oracle Database's flashback capabilities.

1. How Oracle Database Flashback Features can Save Your Job?
08/07/2020
Tércio Costa

2. Tércio Costa
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5. Why Flashback?

6. Flashback Technology
• Perform queries that return past data
• Perform queries that return metadata that shows a detailed history of changes
to the database
• Recover tables or rows to a previous point in time
• Automatically track and archive transactional data changes
• Roll back a transaction and its dependent transactions while the database
remains online

7. How
Flashback
Works?

8. Flashback
Features
• Oracle Flashback Query
• Oracle Flashback Version Query
• Oracle Flashback Transaction Query
• Oracle Flashback Transaction
• DBMS_FLASHBACK Package
• Oracle Flashback Data Archive
• Oracle Flashback Table
• Oracle Flashback Drop
• Oracle Flashback Database

9. Flashback Query
SELECT AS OF
Requirements:
• FLASHBACK Privilege
Example:
SELECT *
FROM employees
AS OF TIMESTAMP
TO_TIMESTAMP('2004-04-04
09:30:00', 'YYYY-MM-DD
HH:MI:SS')
WHERE last_name = 'Chung';

10. Flashback Version Query
VERSIONS BETWEEN { SCN | TIMESTAMP }
start AND end
Example:
SELECT versions_startscn,
versions_starttime,
versions_endscn, versions_endtime,
versions_xid, versions_operation,
last_name, salary
FROM employees
VERSIONS BETWEEN TIMESTAMP
TO_TIMESTAMP('2008-12-18 14:00:00',
'YYYY-MM-DD HH24:MI:SS')
AND TO_TIMESTAMP('2008-12-18
17:00:00', 'YYYY-MM-DD HH24:MI:SS')
WHERE first_name = 'John';
Pseudocolumns:
• VERSIONS_STARTSCN
• VERSIONS_STARTTIME
• VERSIONS_ENDSCN
• VERSIONS_ENDTIME
• VERSIONS_XID
• VERSIONS_OPERATION
Requirements:
• FLASHBACK Privilege

11. Oracle Flashback Transaction Query
View:
FLASHBACK_TRANSACTION_QUERY
Requeriments:
• SUPPLEMENTAL LOG DATA;
• SUPPLEMENTAL LOG DATA (PRIMARY
KEY)
• SUPPLEMENTAL LOG DATA (FOREIGN
KEY)
• SELECT ANY TRANSACTION Privilege
OR FLASHBACK AND READ OR SELECT
Example:
SELECT xid, operation, start_scn,
commit_scn, logon_user, undo_sql
FROM flashback_transaction_query
WHERE xid =
HEXTORAW('000200030000002D')
;

12. DBMS_FLASHBACK
DBMS_FLASHBACK Package
Requirements:
• EXECUTE
ON DBMS_FLASHBACK Privilege
Example(Procedures):
ENABLE_AT_TIME
ENABLE_AT_SYSTEM_CHANGE_NUMBER

14. Flashback Transaction
DBMS_FLASHBACK Package
Requeriments:
• EXECUTE
ON DBMS_FLASHBACK Privilege
• ALTER DATABASE ADD
SUPPLEMENTAL LOG DATA
(PRIMARY KEY) COLUMNS;
• ALTER DATABASE ADD
SUPPLEMENTAL LOG DATA
(FOREIGN KEY) COLUMNS;
Example(procedure):
• TRANSACTION_BACKOUT
Views:
• DBA_FLASHBACK_TXN_STATE
• DBA_FLASHBACK_TXN_REPORT

15. Flashback Data Archive
Once the undo information is lost, the
view of the past is lost also
Privileges:
• FLASHBACK ARCHIVE ADMINISTER
• CREATE FLASHBACK ARCHIVE
• ALTER FLASHBACK ARCHIVE
• DROP FLASHBACK ARCHIVE
• FLASHBACK ARCHIVE object
Package
• DBMS_FLASHBACK_ARCHIVE
Requirements:
• Name of the first tablespace of the Flas
hback Data Archive
• Name of the Flashback Data Archive
• Quota (optional)
• Retention time
• Optimize
Views:
• DBA_FLASHBACK_ARCHIVE
• DBA_FLASHBACK_ARCHIVE_TS
• DBA_FLASHBACK_ARCHIVE_TABLES

16. Flashback Table
Flashback the entire table.
Privileges:
• FLASHBACK ANY TABLE OR
FLASHBACK OBJECT
• READ or SELECT, INSERT, DELETE,
and ALTER privileges on the table
Requirements:
• ROW MOVEMENT (rowids)
Example:
• FLASHBACK TABLE hr.employees TO
TIMESTAMP TO_TIMESTAMP('2013-
10-17 09:30:00', 'YYYY-MM-DD
HH:MI:SS');
Can flashback to time, scn and restore
point.

17. Flashback Drop
Database parameter: recyclebin.
Not a basic parameter!
Do not use UNDO!
The table is only renamed on drop!
Privileges:
• DROP
• READ or SELECT and FLASHBACK
Requirements:
• ALTER SYSTEM SET RECYCLEBIN='on'
SCOPE=SPFILE;
Views:
• RECYCLEBIN
• USER_RECYCLEBIN
• DBA_RECYCLEBIN
• (SHOW RECYCLEBIN)

18. Flashback Database
Flashback the entire database!
Use Flashback logs
Offline operation
Privileges:
• SYSDBA, SYSBACKUP OR SYSDG
View:
• V$FLASHBACK_DATABASE_LOG
Requirements.
• FRA Configured (OMF)
• ARCHIVELOG
• ALTER DATABASE FLASHBACK ON;
Parameter:
• DB_FLASHBACK_RETENTION_TARGET

19. Best Pratices
• UNDO RETENTION
• UNDO TABLESPACE SIZE
• ADD SUPPLEMENTAL LOG DATA AT LEAST
• DOT NOT USE TRIGGERS FOR LOG. USE FLASHBACK DATA ARCHIVE!
• CREATE YOUR OWN INDICES ON FLASBACK DATA ARCHIVE BASE TABLES
• ENABLE RECYCLEBIN
• ENABLE FLASHBACK DATABASE

20. FLASHBACK <> DBPITR
• Media recovery
• Time
• Logical <> phisical
• Redo, Undo and Flashback logs <> backupsets and image copies

21. References
• https://docs.oracle.com/en/database/oracle/oracle-
database/19/sqlrf/FLASHBACK-DATABASE.htm
• https://docs.oracle.com/en/database/oracle/oracle-database/19/bradv/rman-
performing-flashback-dbpitr.html
• https://docs.oracle.com/en/database/oracle/oracle-
database/19/adfns/flashback.html