Les 11 fl2

11
Copyright © 2009, Oracle. All rights reserved.
Using Flashback Technology II

Copyright © 2009, Oracle. All rights reserved.11 - 2
Objectives
After completing this lesson, you should be able to:
• Describe and use Oracle Total Recall
– Creating and enabling a Flashback Data Archive (FDA)
– Managing FDAs
– Viewing metadata
• Describe and use flashback recycle bins
– Restore dropped tables from the recycle bin
– Manage space usage in the recycle bin
– Query the recycle bin
> Total Recall
Flashback Drop

Oracle Total Recall Overview
Automated tracking of historical database changes:
• Enable at the table level with your specified retention
period.
• All subsequent changes are transparently stored and
tamper proof.
• Records older than retention period are automatically
removed.
• Use Flashback technologies to retrieve history.
SELECT … AS OF TIMESTAMP…
SELECT … VERSIONS BETWEEN TIMESTAMP and TIMESTAMP…
updates history queriesBase
Table
Flashback
Data
Archive
Use Cases for Flashback request:
Audit, compliance, historical
reports, ILM

Setup Process
1. Create a new tablespace to hold the FDA.
2. With the FLASHBACK ARCHIVE ADMINISTER system
privilege: Create a Flashback Data Archive, assign it to the
tablespace, and specify its retention period.
3. With the FLASHBACK ARCHIVE object privilege: Alter the
base tables to enable archiving and assign it to a flashback
archive.
ALTER TABLE HR.EMPLOYEES FLASHBACK ARCHIVE fda1;
CREATE FLASHBACK ARCHIVE fda1
TABLESPACE fda_tbs1 QUOTA 10M RETENTION 1 YEAR;
Flashback
Data
ArchiveBase
table

How Total Recall Works
History data:
• Row captured asynchronously by background
processes at self-tuned intervals (default: 5 min)
• Stored compressed and partitioned
• Partitions automatically created
based on time and volume
• Unrelated partitions skipped by
queries
Original data in
buffer cache
fbda slaves (as needed)
. . .
EMPLOYEES FDA1
DMLDML
Undo
data
undo
fbda background
process help
history data
• Automatically purged per
retention policy

Oracle Total Recall Scenario
Using Flashback Data Archive to access historical data:
-- create the Flashback Data Archive
CREATE FLASHBACK ARCHIVE DEFAULT fla1
TABLESPACE tbs1 QUOTA 10G RETENTION 5 YEAR;
-- Enable Flashback Data Archive
ALTER TABLE inventory FLASHBACK ARCHIVE;
ALTER TABLE stock_data FLASHBACK ARCHIVE;
SELECT product_number, product_name, count FROM inventory AS OF
TIMESTAMP TO_TIMESTAMP ('2007-01-01 00:00:00', 'YYYY-MM-DD
HH24:MI:SS');
-- Specify the default Flashback Data Archive
ALTER FLASHBACK ARCHIVE fla1 SET DEFAULT;
1
2
3

Oracle Total Recall Scenario
Optionally, adding space:
ALTER FLASHBACK ARCHIVE fla1
ADD TABLESPACE tbs3 QUOTA 5G;
Optionally, purging data:
ALTER FLASHBACK ARCHIVE fla1 PURGE BEFORE TIMESTAMP
(SYSTIMESTAMP - INTERVAL '1' day);
ALTER FLASHBACK ARCHIVE fla1 MODIFY RETENTION 2 YEAR;
Optionally, changing retention time:
DROP FLASHBACK ARCHIVE fla1;
Optionally, dropping a Flashback Data Archive:
4
5
6
7

Transparent Schema Evolution
• DDL support for:
– Add, drop, rename, and modify column
– Drop and truncate partition
– Rename and truncate table
• Flashback queries work across DDL changes.
• All other DDL is not automatically supported (see next
slide).
Flashback Version Query
DropColumn
time
Addcolumn1
2
3
1
2
3

Full Schema Evolution
Disassociate or associate procedures in the
DBMS_FLASHBACK_ARCHIVE package:
• Disable Total Recall on specified tables and allow more
complex DDL (upgrades, split tables, and so on).
• Enforce schema integrity during association. (Base table
and history table must be the same schema.)
Note: This function should be used with care and with the
understanding that the archive can no longer be guaranteed to
be immutable because the history could have been altered
during the time of disassociation.
associate
disassociate
History
Table History
Table
Base
TableAlter schema
Alter schema
4
1 2
3

Restrictions
• You cannot enable Total Recall for base tables with Hybrid
Columnar compression.
• If disassociate is used, immutability of history is no longer
guaranteed (but you could always purge history previously
anyway with the right privilege).
• There is no transportability of history tables.

Guidelines
• Use SCN for precise queries.
or
• Use Flashback technology for your convenience.
• Flashback uses current system settings.
• Ensure database consistency with a COMMIT or ROLLBACK
operation before querying past data.
• You cannot retrieve past data from a dynamic performance
(V$) view. They contain current data.
• However, you can perform queries on past data in static
data dictionary views, such as *_TABLES.

Viewing Flashback Data Archives
Viewing the results:
View Name (DBA/USER) Description
*_FLASHBACK_ARCHIVE Displays information about Flashback
Data Archives
*_FLASHBACK_ARCHIVE_TS Displays tablespaces of Flashback Data
Archives
*_FLASHBACK_ARCHIVE_TABLES Displays information about tables that are
enabled for flashback archiving

Quiz
You cannot drop, but you can truncate, a table that is tracked
by Oracle Total Recall.
1. True
2. False

Quiz
Select all correct statements about Oracle Total Recall:
1. Oracle Total Recall is enabled by default.
2. A Flashback Data Archive provides the ability to track and
store all transactional changes to a “tracked” table over its
lifetime.
3. Dropping a column in a table enabled for Flashback Data
Archive causes an error.
4. Flashback processing always uses the settings that were
in effect at the time of being queried.
5. Flashback uses the current session settings, such as
national language and character set.

Flashback Drop
and the Recycle Bin
DROP TABLE employees; FLASHBACK TABLE
employees
TO BEFORE DROP;
By mistake
RECYCLEBIN=ON
Total Recall
> Flashback Drop

3
1
Recycle Bin
DROP TABLE employees;
BIN$zbjra9wy==$0EMPLOYEES_PK
EMPLOYEES
Recycle
bin
DBA_FREE_SPACE
BIN$zbjrBdpw==$0
BIN$zbjrBdpw==$0 EMPLOYEES
BIN$zbjra9wy==$0 EMPLOYEES_PK
4
Objects are:
– Renamed
– Not moved
2

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$zbjra9wy==$0
BIN$zbjrBdpw==$0
1
2
3
Recycle bin
DBA_FREE_SPACE - RECYCLEBIN
Autoextend
BIN$zbjrBdpw==$0
BIN$zbjra9wy==$0

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] ;
ALTER SYSTEM SET RECYCLEBIN=OFF SCOPE=SPFILE;
Security considerations for the recycle bin:

Querying the Recycle Bin
SELECT owner, original_name, object_name,
type, ts_name, droptime, related, space
FROM dba_recyclebin
WHERE can_undrop = 'YES';
SQL> SELECT original_name, object_name, ts_name, droptime
FROM user_recyclebin WHERE can_undrop = 'YES';
ORIGINAL_NAME OBJECT_NAME TS_NAM DROPTIME
------------- ----------------------- ------ -------------------
EMPLOYEES2 BIN$NE4Rk64w...gbpQ==$0 USERS 2007-07-02:15:45:13
SQL> SHOW RECYCLEBIN

Quiz
When you flash back a dropped table, the recovered indexes,
triggers, and constraints keep their recycle bin names.
1. True
2. False

Summary
In this lesson, you should have learned how to:
• Set up and use Total Recall
• Restore dropped tables from the recycle bin
• Query the recycle bin

Practice 11 Overview:
Using Flashback Technology
This practice covers the following topics:
• Using Total Recall
• Recycle bin activities (optional)

Les 11 fl2

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