Are You Using Flashback Yet?

1. Are You Using Flashback Yet?
Biju Thomas
OneNeck IT Services Corporation
http://www.oneneck.com (Booth 4364)
Session #330

2. About the Speaker
• Senior Database Administrator at OneNeck
IT Services Corporation (www.oneneck.com)
• More than 15 years of Oracle experience
• Author of OCA Oracle Database 11g Administrator
Certified Associate Study Guide published by Sybex
• Co-author of Oracle10g, Oracle9i & Oracle8i
Certification books published by Sybex
• Published articles in Oracle Magazine, Oracle
Internals and Select Journal
• Oracle 11g, 10g, 9i, 8i & 7.3
OCP Administrator

3. Introducing OneNeck
The ERP Outsourcing Experts
Provide a comprehensive, flexible suite of outsourcing
solutions designed specifically to help mid-market and
public sector organizations
• Supporting over 22,000 users at over 850 sites worldwide
• Primary data center/support center operations in Phoenix
and Houston
• Hosting and managing over 2000 databases
• 98% Contract Renewal Rate over 10 years
• 100% US based operations and staff
• 24x7x365 support center handling over 50,000 tickets
annually
• Oracle certified hosting partner
• Ranked #1 ERP Outsourcing Vendor by the Black Book of
Outsourcing three years in a row
• http://www.OneNeck.com
• Stop by booth 4364

4. Please remember to complete the
session evaluation form
Biju Thomas
Are you using Flashback yet?
Session # 330

5. Objectives
• Flashback Operations in Oracle Database
• What is Flash Recovery Area (FRA)?
• Configuring FRA
• Flashback Database
• Using & Maintaining FRA
• V$ Views for FRA and Flashback logs

6. Flashback Operations in Oracle

7. Flashback Query
• Introduced in Oracle 9i R1
• Use DBMS_FLASHBACK package to enable
and disable flashback
• Must use Automatic Undo Management
• Only DML operations
• PL/SQL recognizes flashback
EXECUTE DBMS_FLASHBACK.ENABLE_AT_SYSTEM_CHANGE_NUMBER (n);
EXECUTE DBMS_FLASHBACK.ENABLE_AT_TIME (‘date_time‘);
EXECUTE DBMS_FLASHBACK.DISABLE;

8. Flashback Query #2
• Improvement in 9i R2
• AS OF TIMESTAMP and AS OF SCN clauses in query
• SYS user can use this clause
Examples:
INSERT INTO employees
SELECT * FROM employees as of timestamp
TO_TIMESTAMP('22-MAR-09 21:50', 'DD-MON-YY HH24:MI')
WHERE employee_id = 106;
EXP Parameter:
FLASHBACK_SCN=nnn
FLASHBACK_TIME="YYYY-MM-DD HH24:MI:SS" [9i fixed format]
FLASHBACK_TIME="TO_TIMESTAMP('31-MAR-09 12:00', 'DD-MON-YY
HH24:MI')" [specify format 10g onwards]

9. Flashback Query #3
• Example: Rows updated in EMPLOYEES table.
SELECT employee_id, first_name, last_name, salary
FROM employees AS OF TIMESTAMP
TO_TIMESTAMP('22-MAR-09 21:50', 'DD-MON-YY HH24:MI')
MINUS
SELECT employee_id, first_name, last_name, salary
FROM employees;
EMPLOYEE_ID FIRST_NAME LAST_NAME SALARY
----------- ------------- ---------------- ----------
103 Alexander Hunold 9000
106 Valli Pataballa 4800

10. Flashback Versions Query
• Introduced in Oracle 10g R1
• Shows all changes between a timeframe
VERSIONS BETWEEN [TIMESTAMP/SCN] .. AND ..
• Upper/Lower bound may be replaced with
MINVALUE and MAXVALUE to retrieve all
available data
• VERSIONS_ pseudo columns available –
STARTTIME, STARTSCN, ENDTIME,
ENDSCN, XID, OPERATION

11. Flashback Versions Query #2
• Example:
SELECT last_name, versions_starttime,
versions_endtime, versions_operation
FROM employees VERSIONS BETWEEN TIMESTAMP minvalue AND maxvalue
WHERE employee_id = 106
ORDER BY versions_starttime NULLS FIRST;
LAST_NAME VERSIONS_STARTTIME VERSIONS_ENDTIME V
------------- ---------------------- ---------------------- -
Pataballa 22-MAR-09 09.54.57 PM
Rojashin 22-MAR-09 09.54.57 PM 22-MAR-09 10.07.06 PM U
Hussaina 22-MAR-09 10.07.06 PM 22-MAR-09 10.14.04 PM U
Hussaina 22-MAR-09 10.14.04 PM D
Pataballa 22-MAR-09 10.17.21 PM I

12. Flashback Transaction Query
FLASHBACK_TRANSACTION_QUERY
• Introduced in Oracle 10g R1
XID
• Enterprise Edition only START_SCN
• Changes made to data at a START_TIMESTAMP
transaction level COMMIT_SCN
COMMIT_TIMESTAMP
• No need to use LogMiner LOGON_USER
• Reconstruct SQL to undo UNDO_CHANGE#
changes OPERATION
TABLE_NAME
• Need FLASHBACK ANY
TABLE_OWNER
TRANSACTON system privilege
ROW_ID
to query view UNDO_SQL
FLASHBACK_TRANSACTION_
QUERY

13. Flashback Transaction Query #2
SELECT operation, start_timestamp, undo_sql
FROM flashback_transaction_query
WHERE table_name = 'EMPLOYEES'
AND table_owner = 'HR';
OPERATION START_TIMESTAMP
UNDO_SQL
------------------------------------------------------
UPDATE 22-MAR-09 21:53:21
update "HR"."EMPLOYEES" set "FIRST_NAME" = 'Alexander', "SALARY" = '9000'
where ROWID = 'AAARAIAAFAAAABXAAD';
DELETE 22-MAR-09 22:14:04
insert into "HR"."EMPLOYEES“ ("EMPLOYEE_ID", "FIRST_NAME", "LAST_NAME“
,"EMAIL", "PHONE_NUMBER", "HIRE_DATE", "JOB_ID", "SALARY",
"COMMISSION_PCT", "MANAGER_ID", "DEPARTMENT_ID") values ('106', 'Valli',
'Hussaina', 'VPATABAL', '590.423.4560',TO_DATE('05-FEB-98 00:00:00', 'DD-
MON-YY HH24:MI:SS'),'IT_PROG','4800',NULL,'103','60');
INSERT 22-MAR-09 22:17:13
delete from "HR"."EMPLOYEES" where ROWID = 'AAARAIAAFAAAABYAAJ';

14. Flashback Table (Drop)
• Introduced in Oracle 10g R1 (EE)
• Recover a dropped table (does not use UNDO)
DROP TABLE job_history;
Table dropped.
SHOW RECYCLEBIN
ORIGINAL NAME RECYCLEBIN NAME OBJECT TYPE DROP TIME
-------------- ------------------------------ ------------ -------------------
JOB_HISTORY BIN$ZcGwtQ/sKCbgQAB/AQBl2g==$0 TABLE 2009-03-22:23:27:54
FLASHBACK TABLE job_history TO BEFORE DROP;
Flashback complete.
• Option to rename table
FLASHBACK TABLE jobs TO BEFORE DROP RENAME TO jobs_march;

15. Flashback Drop #2
• Recycle bin automatically cleared when
tablespace is under “space pressure”
• Options for manually clearing space:
PURGE TABLE <name> PURGE RECYCLEBIN
PURGE INDEX <name> PURGE DBA_RECYCLEBIN
PURGE TABLESPACE <name> DROP TABLE <name> PURGE
PURGE TABLESPACE <name>
USER <name>
• To disable recyclebin:
– 10gR1: _recyclebin parameter
– 10gR2+: recyclebin parameter

16. Flashback Table #3
• Reinstate table to a previous state using
TIMESTAMP or SCN (uses UNDO)
• ROW MOVEMENT should be enabled.
ALTER TABLE employees ENABLE ROW MOVEMENT;
Table altered.
FLASHBACK TABLE employees TO TIMESTAMP
TO_TIMESTAMP('22-MAR-09 21:50', 'DD-MON-YY HH24:MI');
Flashback complete.

17. Flashback Database
• Introduced in Oracle 10g R1 (EE)
• Quickly rewind a database to fix any issues
• Similar to point-in-time recovery, but much
faster
• Uses flashback logs, a before image of
changed blocks
• Flashback logs saved in Flash Recovery Area
(FRA)
• 10g R2 introduced restore points and the
ability to flashback through RESETLOGS

18. Flashback Transaction
• Introduced in Oracle 11g R1 (EE)
• Use to undo changes made by transaction
• Uses UNDO and redo logs (archive logs too)
• Requires supplemental logging of primary key
ALTER DATABASE ADD SUPPLEMENTAL LOG DATA (PRIMARY KEY) COLUMNS;
• Enterprise Manager or PL/SQL interface
– Under “Availability” tab, click “View and Manage
Transactions”
– DBMS_FLASHBACK.TRANSACTION_BACKOUT
procedure

20. Flashback Data Archive
• Introduced in Oracle 11g R1 (EE)
• Total Recall Option – separate license.
• Automatically track and maintain changes to data in
an application transparent and secure manner.
• Uses AS OF construct in SQL.
• Historical data can be kept for any specified duration
– not dependent on undo or flashback log data.
• RETENTION specified in the data archive.
• New background process “fbda” captures historic
information in a non-intrusive manner.
• New record added to history table only for update &
delete statements.

21. Settings for Undo Flashback
• Enabling automatic Undo
– UNDO_MANAGEMENT = AUTO
• Parameters controlling amount of undo retained:
– UNDO_RETENTION
• Guaranteed retention option available
– ALTER TABLESPACE <undots> RETENTION
GUARANTEE
• Flashback Operations using Undo
– FB Query, FB Versions Query, FB Transaction, FB
Transaction Query, FB Table

22. Flash Recovery Area (FRA)

23. Flash Recovery Area
• Area of disk location where recovery related
files are stored
• Managed via Oracle Managed Files
• Free space automatically managed by
Oracle, obsolete files under current retention
policies are deleted when space needed.
• Can act as a disk cache for backup files
before writing to tape
• Flashback logs required to use the Flashback
database feature are created only in FRA

24. Flash Recovery Area #2
• Need to specify the disk quota.
• Preferable to be on a different disk where
database files are not stored.
• Permanent and transient files can be stored –
permanent files are copies of redo logs and
control file.
• FRA can be on ASM disk
• Oracle server alerts monitors the reclaimable
space in FRA

25. Configuring FRA
• DB_RECOVERY_FILE_DEST_SIZE
– Specify the maximum space allocated for FRA
• DB_RECOVERY_FILE_DEST
– Location of the FRA
• For RAC databases, all instances must have
same values
• DB_FLASHBACK_RETENTION_TARGET
– Specify in minutes how much flashback log
information should be retained – Default 1440.

26. FRA Contents
• Permanent Files
– Copy of control file
– Copy of redo log files
• Transient Files
– Archive log files
– Flashback logs
– RMAN control file and spfile autobackup
– RMAN image copies & backup sets
Example File Name:
/u05/flash_recovery_area/11GR11/backupset/2009_03_26/o1_mf_
annnn_TAG20090326T004654_4wp5rntg_.bkp

27. Sizing FRA
• Bigger the FRA, more useful it becomes
• Recommendation: DB Size + Incr backups +
archive logs + flashback logs
• Flashback logs generated are approximately
similar in size to redo logs generated.
• If there is not enough free space in FRA,
flashback logs are deleted to make room.

28. Using Database Flashback

29. Configuring Flashback
• Enable flashback on the database in mount
state.
SHUTDOWN IMMEDIATE;
STARTUP MOUNT;
ALTER DATABASE FLASHBACK ON;
ALTER DATABASE OPEN;
• Flashback logs will be written to FRA, and
oldest logs deleted when FRA becomes full.
• Database must be in ARCHIVELOG mode.

30. Flashback a Database
• To flashback a database is similar to
performing a point-in-time recovery
• RESETLOGS required to open database.
SHUTDOWN IMMEDIATE;
STARTUP MOUNT;
FLASHBACK DATABASE TO [BEFORE] [SCN | TIME |
SEQUENCE ] = value;
ALTER DATABASE OPEN RESETLOGS;
• Archive logs may be used to fill-in the gaps

31. Using Restorepoints
• Introduced in Oracle 10g R2
• Very useful when performing planned
maintenance
• Option to guarantee flashback
CREATE RESTORE POINT before_patch;
CREATE RESTORE POINT before_patch GUARANTEE
FLASHBACK DATABASE;
FLASHBACK DATABASE TO RESTORE POINT before_patch;
DROP RESTORE POINT before_patch;

32. Using Flashback for DR Testing
• Setup FRA and enable flashback logs in the standby
database
• Create a restore point to go back to
• Disable log transport to standby database from primary
• Activate the standby database and open database.
• When testing is completed, revert back to the restore
point using FLASHBACK DATABASE.
• Convert the database to physical standby again
• Catch up the standby database to primary database
• Enable log transport from primary

33. Standby Redo-apply Delay`
• Oracle provides time delay in applying the
archivelogs to the standby database to delay the
propagation of errors and corruption to standby
database.
• By having flashback logging on the standby
database, you can always flashback the standby
database, thus eliminate using time-delay.
• You can flashback and open the standby database,
get the rows/tables that were messed up and put the
standby database back in recovery mode.
• This helps to avoid outage to primary database for
non-critical data recovery.

34. Using and Maintaining FRA

35. Automated RMAN Backups
• When no FORMAT clause is specified for
RMAN backups, they go into FRA.
• Automatic controlfile and spfile backups may
be configured to go to FRA.
• Consider keeping image copies in FRA, with
incrementally updated backups (and with
optional rolling window)
RUN
{ RECOVER COPY OF DATABASE WITH TAG 'daily_incr'
UNTIL TIME 'SYSDATE - 3';
BACKUP INCREMENTAL LEVEL 1 FOR RECOVER OF COPY WITH TAG
'daily_incr' DATABASE;
}

36. RMAN FORMAT Clause
• If you perform RMAN disk backups with the
FORMAT clause specifying the FRA location,
they are not managed by Oracle and not
considered for FRA cleanup and FRA space
management algorithm.
• So, to backup to FRA, do not specify the
FORMAT clause, the default location is the
FRA for RMAN backups when FRA is
configured.
RMAN> CONFIGURE CHANNEL DEVICE TYPE DISK CLEAR;

37. Backing up FRA
• FRA can be backed up only using RMAN
RUN {
ALLOCATE CHANNEL CH01T TYPE sbt_tape;
BACKUP RECOVERY AREA;
}
• Flashback logs, the current control file, and
online redo logs are not backed up.
• This statement can only back up to a tape
device, disk is not supported.

38. Using LOG_ARCHIVE_DEST_n
• If you explicitly specify the FRA location in the
LOG_ARCHIVE_DEST_n parameter, the
archive logs are not considered in the FRA
space management algorithm and they are
not backed up when you specify the BACKUP
RECOVERY AREA command.
• The correct specification is
log_archive_dest_n=
'LOCATION= USE_DB_RECOVERY_FILE_DEST'

39. FRA Full Errors
• Once the Flash Recovery Area is full, Oracle
automatically deletes eligible files to reclaim space in
the Flash Recovery Area as needed.
• Oracle may delete flashback logs from the earliest
SCNs to make room for other files.
• Alert log errors:
ORA-19809: limit exceeded for recovery files
ORA-19804: cannot reclaim <nnnnn> bytes disk
space from <mmmmm> limit
ORA-19815: WARNING: db_recovery_file_dest_size of
<size of FRA configured> bytes is 100.00% used,
and has 0 remaining bytes available.

40. Resolving Full FRA
• Make more space available by adjusting
DB_RECOVERY_FILE_DEST_SIZE.
• Backup the contents of the Flash Recovery
Area to a tertiary device such as tape.
• Change backup retention policy.
CONFIGURE RETENTION POLICY TO RECOVERY WINDOW
OF 7 DAYS;
• Change archive log deletion policy.
CONFIGURE ARCHIVELOG DELETION POLICY TO BACKED
UP 1 TIMES TO SBT;

41. V$ Views

42. Backups/Logs Using FRA
• Find out if backups and archive logs are part
of the FRA algorithm
– IS_RECOVERY_DEST_FILE column in
V$BACKUP_PIECE
– IS_RECOVERY_DEST_FILE column in
V$ARCHIVED_LOG

43. V$RECOVERY_FILE_DEST
• Find out the current location, disk quota, space in
use, space reclaimable by deleting files, and total
number of files in the Flash Recovery Area.
SQL> select * from v$recovery_file_dest;
NAME
SPACE_LIMIT SPACE_USED SPACE_RECLAIMABLE NUMBER_OF_FILES
------------ ------------ ----------------- --------------
/u01/app/oracle/flash_recovery_area
15728640000 9448377344 10272768 213

44. V$FLASH_RECOVERY_AREA_USAGE
• Find out the percentage of the total disk quota used by different
types of files. Determine how much space for each type of file can
be reclaimed by deleting files that are obsolete, redundant, or
already backed up to tape.
SQL> SELECT FILE_TYPE, PERCENT_SPACE_USED USED, PERCENT_SPACE_RECLAIMABLE RECLAIM,
NUMBER_OF_FILES FILES FROM V$FLASH_RECOVERY_AREA_USAGE;
FILE_TYPE USED RECLAIM FILES
-------------------- ---------- ---------- ----------
CONTROL FILE 0 0 0
REDO LOG 0 0 0
ARCHIVED LOG 61.66 51.2 216
BACKUP PIECE 19.07 9.7 31
IMAGE COPY 4.93 .4 8
FLASHBACK LOG 1.24 0 9
FOREIGN ARCHIVED LOG 0 0 0

45. V$FLASHBACK_DATABASE_LOG
• Estimate how far back you can rollback the
database using flashback logs, and estimated
size based on retention target.
SQL> select * from v$flashback_database_log;
OLDEST_FLASHBACK_SCN OLDEST_FL RETENTION_TARGET FLASHBACK_SIZE
-------------------- --------- ---------------- --------------
ESTIMATED_FLASHBACK_SIZE
------------------------
8257936 25-MAR-09 1440 194478080
4303306752

46. Items Learned in this Session
• Flashback Operations
– Think of flashback before saying “no” or getting
ready to recover
• Flash Recovery Area
– It’s worth even if you use it just for flashback logs
– Do not specify FORMAT clause for RMAN or
directory name for archive log destination
• Flashback Database
– Good for critical patching activities, migrations
– Use restorepoints

47. Questions…?

48. Thank You…
• Please complete the session evaluation form
– Biju Thomas
– Are you using Flashback yet?
– Session # 330
• Further questions, comments…
– Stop by Booth # 4364
– WWW.ONENECK.COM