6 Copyright © 2006, Oracle. All rights reserved. Flashback

6Copyright © 2006, Oracle. All rights reserved.

Flashback

6-2 Copyright © 2006, Oracle. All rights reserved.

Objectives

After completing this lesson, you should be able to:

• Query the recycle bin

• Configure Flashback Database

• Perform Flashback Database to a point in time

• Monitor flashback log statistics

• Enable and disable the Flashback Database feature

• Use the Enterprise Manager Recovery Wizard to perform Flashback Database

• Use guaranteed restore points with Flashback Database

Recycle binFlashback DBConfig. FB DBMonitor FB DBGuar. Res. Pt.


Flashback Technology: Review

Object Level Scenario Examples

FlashbackTechnology Uses

AffectsData

Database Truncate table; Undesired multitable changes made

Database Flashback logs

TRUE

Table Drop table Drop Recycle bin TRUE

Update with the wrong WHERE clause

Table Undo data TRUE

Compare current data with data from the past

Query Undo data FALSE

Compare versions of a row

Version Undo data FALSE

Tx Investigate several historical states of data

Transaction Undo data FALSE


Flashback Drop and the Recycle Bin

DROP TABLE employees;

FLASHBACK TABLEemployeesTO BEFORE DROP; Mistake was

made.

RECYCLEBIN=ON


3

21

Recycle Bin

DROP TABLE employees;

BIN$zbjra9wy==$0EMPLOYEES_PK

EMPLOYEES

Recyclebin

DBA_FREE_SPACE

BIN$zbjrBdpw==$0

USER_OBJECTS

BIN$zbjrBdpw==$0 EMPLOYEESBIN$zbjra9wy==$0 EMPLOYEES_PK

4

Objects are:

– Renamed

– Not moved


Restoring Tables from the Recycle Bin

• Restore dropped tables and dependent objects.

• If multiple recycle bin entries have the same original name:– Use unique, system-generated names to restore a

particular version– When using original names, the restored table is

last in, first out (LIFO)

• Rename the original name if that name is currently used.

FLASHBACK TABLE <table_name>TO BEFORE DROP [RENAME TO <new_name>];


Recycle Bin: Automatic Space Reclamation

BIN$zbjrBdpw==$0 BIN$zbjra9wy==$0

BIN$zbjra9wy==$0

BIN$zbjrBdpw==$0

1

2

3

Recycle bin

DBA_FREE_SPACE - RECYCLEBIN

Autoextend


Recycle Bin: Manual Space Reclamation

PURGE {TABLE <table_name>|INDEX <index_name>}

PURGE TABLESPACE <ts_name> [USER <user_name>]

PURGE [USER_|DBA_]RECYCLEBIN


Bypassing the Recycle Bin

DROP TABLESPACE <ts_name> [INCLUDING CONTENTS] ;

DROP USER <user_name> [CASCADE] ;

DROP TABLE <table_name> [PURGE] ;


Querying the Recycle Bin

SELECT owner, original_name, object_name, type, ts_name, droptime, related, spaceFROM dba_recyclebinWHERE can_undrop = 'YES';

SELECT original_name, object_name, type, ts_name, droptime, related, spaceFROM user_recyclebinWHERE can_undrop = 'YES';

SQL> SHOW RECYCLEBIN


Querying Data fromDropped Tables

SELECT ... FROM "BIN$zbjrBdpw==$0" [AS OF ...]WHERE ...

Recyclebin

USER_INDEXES

YES

INDEX_NAMEDROPPED

NO SALES_PK

USER_TABLESTABLE_NAMEDROPPED

YES

NO SALES

BIN$zbjrBdpw==$0 EMPLOYEES

BIN$zbjra9wy==$0 EMPLOYEES_PK


Flashback Database: Review

The Flashback Database operation:

• Works like a rewind button for the database

• Can be used in cases of logical data corruptions made by users

The database is corrupted.

The database is “rewound.”

You “press the rewind button.”

Users generate errors.

Recycle bin> Flashback DB

Config. FB DBMonitor FB DBGuar. Res. Pt.


Flashback Database Architecture

Flashbackbuffer

Redo logbuffer

SGA

LGWR

RVWRFlashbacklogs

Redologs

… …

Buffer cache

1

Log blockbeforeimages

periodically.

Back out changesto database using

before images.

Do forward media recovery.

Everychange

Not everychange!

2


Configuring FlashbackDatabase

1. Configure the flash recovery area.

3. Enable Flashback Database.

2. Set the retentiontarget.

SQL> SHUTDOWN IMMEDIATE;SQL> STARTUP MOUNT EXCLUSIVE;SQL> ALTER SYSTEM SET

2 DB_FLASHBACK_RETENTION_TARGET=2880 SCOPE=BOTH;

SQL> ALTER DATABASE FLASHBACK ON;SQL> ALTER DATABASE OPEN;

Recycle binFlashback DB

> Config. FB DBMonitor FB DBGuar. Res. Pt.


Configuring Flashback Database Using EM

Make sure that the database is in ARCHIVELOG mode.


Configuring Flashback Database Using EM

Enable flashback logging and specify the flash recovery area.


Flashback Database: Examples

RMAN> FLASHBACK DATABASE TO TIME = 2> "TO_DATE('2004-05-27 16:00:00', 3> 'YYYY-MM-DD HH24:MI:SS')";

RMAN> FLASHBACK DATABASE TO SCN=23565;

RMAN> FLASHBACK DATABASE 2> TO SEQUENCE=223 THREAD=1;

SQL> FLASHBACK DATABASE 2 TO TIMESTAMP(SYSDATE-1/24);

SQL> FLASHBACK DATABASE TO SCN 53943;

SQL> FLASHBACK DATABASE TO RESTORE POINT b4_load;


Performing Flashback Database Using EM

Select object and

operation type.



Launching the Recovery Wizard:




Excluding Tablespaces from Flashback Database

• Take the tablespace offline before you perform the Flashback Database recovery.

• Drop the tablespace or recover the offline files with traditional point-in-time recovery.

ALTER TABLESPACE <ts_name> FLASHBACK {ON|OFF}

SQL> SELECT name, flashback_on 2 FROM v$tablespace;


Flashback Database Considerations

• When the Flashback Database operation completes, open the database:– In read-only mode to verify that the correct target

time or SCN was used– With a RESETLOGS operation to allow for DML

• The opposite of “flash back” is “recover.”

• You cannot use Flashback Database in the following situations:– The control file has been restored or re-created.– A tablespace has been dropped.– A data file has been shrunk.

• Use the TO BEFORE RESETLOGS to flash back to before the last RESETLOGS operation.


Monitoring FlashbackDatabase

To monitor the ability to meet your retention target:

• View the flash recovery area disk quota:

• Determine the current flashback window:

• Monitor logging in the Flashback Database logs:

SQL> SELECT estimated_flashback_size, 2 flashback_size 3 FROM V$FLASHBACK_DATABASE_LOG;

SQL> SELECT * 2 FROM V$FLASHBACK_DATABASE_STAT;

SQL> SELECT oldest_flashback_scn, 2 oldest_flashback_time 3 FROM V$FLASHBACK_DATABASE_LOG;

Recycle binFlashback DBConfig. FB DB

> Monitor FB DBGuar. Res. Pt.


Monitoring Flashback Database with EM


Guaranteed Restore Points

A guaranteed restore point ensures that you can perform a FLASHBACK DATABASE command to that SCN at any time.

SQL> CREATE RESTORE POINT before_load

2 GUARANTEE FLASHBACK DATABASE;

Recycle binFlashback DBConfig. FB DBMonitor FB DB

> Guar. Res. Pt.


Summary

In this lesson, you should have learned how to:

• Query the recycle bin

• Configure Flashback Database

• Perform Flashback Database to a point in time using Enterprise Manager or RMAN

• Monitor flashback log statistics

• Enable and disable the Flashback Database feature

• Use guaranteed restore points with Flashback Database


Practice Overview: Performing Flashback Database

This practice covers the following topics:

• Performing Flashback Database to undo unwanted transactions

• Monitoring the Flashback Database retention

• Determine the size of the flashback logs

Documents

6 Copyright © 2006, Oracle. All rights reserved. Flashback