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Oracle10g: Behind the Scenes of

Flashback Technologies

DOUG MeetingJuly 19, 2007

Kirtikumar Deshpande

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About Me Senior Oracle DBA

Idearc Media

Phone Directories Publication

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Agenda Flashback Query - Background Oracle10g - What’s New Flashback Table Flashback Drop Table Flashback Version Query Flashback Transaction Query Flashback Database Q & A

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Flashback Query - Background Oracle9i Release 1

Undo Tablespace Automatic Undo Segments Undo Retention Time Session level Flashback Query feature

Oracle9i Release 2 Statement level Flashback Query

feature

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What’s New in Oracle10g Guaranteed Undo Retention

Undo preserved for specified retention time

Auto Undo Retention Tuning Undo Retention time adjusted

automatically V$UNDOSTAT view enhancements

New information to track long running queries

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What’s New in Oracle10g Pseudocolumns

ORA_ROWSCN VERSIONS_STARTTIME VERSIONS_STARTSCN VERSIONS_ENDTIME VERSIONS_ENDSCN VERISONS_XID VERSIONS_OPERATION

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What’s New in Oracle10g Functions

SCN_TO_TIMESTAMP TIMESTAMP_TO_SCN

View FLASHBACK_TRANSACTION_QUERY

Recycle Bin To restore dropped table (not

PURGED)

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What’s New in Oracle10g Flashback Drop

Restore dropped table

Flashback Table Restore table to a point in time in the

past

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What’s New in Oracle10g Flashback Versions Query

How data changed over a timeframe

Flashback Transaction Query How data changed at transactions

level

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What’s New in Oracle10g Flashback Database

Restores database to a point in time in the past

Does not use undo segments and recyclebin

Needs special configuration

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Guaranteed Undo Retention Guaranteed Retention makes sure

that the committed undo is preserved for the specified retention time.

Transactions that need more undo space may terminate due to lack of undo space as Oracle will not overwrite undo information.

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Guaranteed Undo Retention

UNDO Tablespace Option create unto tablespace undo_tbs datafile ‘/u09/oradata/ked9_undo_01.dbf’ size

100M retention guarantee;

alter tablespace undo_tbs retention guarantee; alter tablespace undo_tbs retention noguarantee;

RETENTION NOGUARANTEE - Default

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Auto Undo Retention Tuning UNDO_RETENTION value may

change

V$UNDOSTAT tracks undo retention value for sampled intervals TUNED_UNDORETENTION

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V$UNDOSTAT View New Columns

MAXQUERYID ACTIVEBLKS UNEXPIREDBLKS EXPIREDBLKS TUNED_UNDORETENTION

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V$UNDOSTAT ExampleBEGIN_TIME END_TIME MAXQUERYID MAXQL TUNEDRET ACTBLK UNXPBLK XPBLK------------------------ ------------------------- ------------------- ----------- -------------- ---------- ----------- ---------- 22-FEB-06 23:54:49 23-FEB-06 00:04:49 0 1800 448 256 142416 22-FEB-06 23:44:49 22-FEB-06 23:54:49 0 1800 448 130176 12496 22-FEB-06 23:34:49 22-FEB-06 23:44:49 b1z64uk2y5p6v 5997 6358 448 130048 12496 22-FEB-06 23:24:49 22-FEB-06 23:34:49 b1z64uk2y5p6v 5392 5752 448 130048 12496 22-FEB-06 23:14:49 22-FEB-06 23:24:49 b1z64uk2y5p6v 4785 5145 448 130048 12496 22-FEB-06 23:04:49 22-FEB-06 23:14:49 b1z64uk2y5p6v 4178 4538 448 130048 12496 22-FEB-06 22:54:49 22-FEB-06 23:04:49 b1z64uk2y5p6v 3571 3932 448 129792 12496 22-FEB-06 22:44:49 22-FEB-06 22:54:49 b1z64uk2y5p6v 2965 3325 448 129664 12496 22-FEB-06 22:34:49 22-FEB-06 22:44:49 b1z64uk2y5p6v 2357 2720 448 129408 13392 22-FEB-06 22:24:49 22-FEB-06 22:34:49 b1z64uk2y5p6v 1752 2112 448 129408 13264 22-FEB-06 22:14:49 22-FEB-06 22:24:49 b1z64uk2y5p6v 1145 1800 448 129408 13136 22-FEB-06 22:04:49 22-FEB-06 22:14:49 b1z64uk2y5p6v 538 1800 448 127616 13264 22-FEB-06 21:54:49 22-FEB-06 22:04:49 5rv0j37z1ztgm 203 1800 448 256 15952 22-FEB-06 21:44:49 22-FEB-06 21:54:49 ac20brc1kdgdx 927 1800 448 256 15952 22-FEB-06 21:34:49 22-FEB-06 21:44:49 ac20brc1kdgdx 320 1800 448 128 16080

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Flashback Table Recovers table data to point in

time in the past Uses undo segments to reconstruct

past data Undo information must be

available in undo segments Uses an internal global temporary

table, SYS_TEMP_FBT, to stage data

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Flashback Table Enable row movement

alter table t1 enable row movement; Flashback Table to SCN or

Timestamp flashback table t1 to <SCN>; flashback table t1 to timestamp( <systimestamp – interval ‘5’

minute>);

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Flashback Table Example:

SQL> select department_id, department_name from dept;

DEPARTMENT_ID DEPARTMENT_NAME

--------------------- ------------------------------ 10 Administration

20 Marketing 30 Purchasing 40 Human Resources

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Flashback TableSQL> delete dept;4 rows deleted.SQL> commit;Commit complete.

SQL> flashback table dept to timestamp (systimestamp - interval ‘10' minute);

Flashback complete.

SQL> select department_id, department_name from dept;

DEPARTMENT_ID DEPARTMENT_NAME --------------------- ------------------------------ 10 Administration 20 Marketing 30 Purchasing 40 Human Resources

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Flashback Table Restrictions and Limitations

Does not work for Clustered tables Tables in Materialized View Advance Queuing Tables Data Dictionary Tables Table Partitions/Sub-Partitions Nested Tables Remote Tables

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Flashback Table Restrictions and Limitations

Referential Integrity Constraints may limit flashback operation

Any DDL operation on table will restrict flashback time (or SCN) to the DDL time

Bug: 3076151 - Unpublished Internal GTT SYS_TEMP_FBT not

dropped after flashback operation

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Flashback Drop Table Really an ‘undrop’ Table operation Does not use Undo Segments Uses ‘RECYCLEBIN’ to restore a

dropped tableflashback table t1 to before drop; flashback table t1 to before drop

rename t2;

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Flashback Drop Table DROP TABLE with PURGE option, or

purging RECYCLEBIN will NOT restore the table

Restored dependent objects (triggers, indexes, constraints) will get system generated names Need to RENAME those explicitly

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Flashback Drop Table Recyclebin

Dropped objects do not release disk space

Views USER_RECYCLEBIN DBA_RECYCLEBIN

Public Synonym RECYCLEBIN

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Flashback Drop Table Recyclebin

Enabled by Default Can be Disabled

10g R1 alter system set “_recyclebin” = false; 10g R2 alter session set recyclebin = off; alter system set recyclebin = off;

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Flashback Drop Table Example:

SQL> drop table fdt cascade constraints;Table dropped.

SQL> select object_name, original_name, type from recyclebin; OBJECT_NAME ORIGINAL_NAME TYPE ---------------------------------------------- --------------------- -------------- BIN$2NkxhR9EQYaOi6iEb5MyEw==$0 FDT_I1 INDEX BIN$eH23RoJUSg6P6x98+kvK/w==$0 FDT_PK INDEX BIN$3jL+fbUZTza4Z0HRlZMYvA==$0 FDT_T1 TRIGGER BIN$2EIiiDRWQ8u/P1c366iICg==$0 FDT TABLE

4 rows selected.

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Flashback Drop TableSQL> flashback table fdt to before drop;Flashback complete.SQL> select index_name obj_name, ‘NDX' type from user_indexes where table_name ='FDT‘ 2 union 3 select trigger_name obj_name, 'TRIG' type from user_triggers where table_name =

'FDT' 4 union 5 select constraint_name obj_name, 'CNSTR- ' ||constraint_type 6 from user_constraints where table_name = 'FDT' 7 /OBJ_NAME TYPE------------------------------------------------ ---------------BIN$2NkxhR9EQYaOi6iEb5MyEw==$0 NDXBIN$3jL+fbUZTza4Z0HRlZMYvA==$0 TRIGBIN$ZsANcV+8TfGmDzwH5wzIFg==$0 CNSTR- PBIN$eH23RoJUSg6P6x98+kvK/w==$0 NDXBIN$s10Y+0xMTriID+82Iqovxg==$0 CNSTR- C5 rows selected.

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Flashback Drop Table Limitations (Does not Work For)

External Tables Materialized Views Tables in Dictionary Managed

Tablespaces Tables in SYSTEM Tablespace

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Flashback Versions Query View row data at various commit

times (Versions) within a timeframe Enhanced SQL syntax to retrieve

rows VERSIONS BETWEEN Clause

Timeframe can be Timestamp range or SCN range VERSIONS BETWEEN TIMESTAMP VERSIONS BETWEEN SCN

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Flashback Versions Query Timeframe must fall within Undo

Retention time Can be used to audit and analyze

changes Can assist in testing Application

process Only committed changes can be

seen

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Flashback Versions Query Syntax:

SELECT * FROM DEPARTMENTSVERSIONS BETWEEN TIMESTAMP

(SYSTIMESTAMP – INTERVAL ’30’ MINUTE) AND

(SYSTIMESTAMP)WHERE DEPARTMENT_ID = 100;

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Flashback Versions Query Pseudo-columns with returned rows:

VERSIONS_STARTSCN If NULL, then version existed prior to the

lower bound of SCN range, else the starting SCN for version of row data shown

VERSIONS_ENDSCN If NULL, then shown version is current row

or row is deleted, else the SCN when row version expired

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Flashback Versions Query Pseudo-columns:

VERSIONS_STARTTIME If NULL then version existed prior to the

lower bound of timestamp range, else the starting timestamp for version of row data shown

VERSIONS_ENDTIME If NULL then shown version is current row

or row is deleted, else the timestamp when row version expired

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Flashback Versions Query Pseudo-columns:

VERSIONS_XID Transaction ID that created the row

version VERSIONS_OPERATION

DML Operation that created the row version (I=Insert, D=Delete, U=Update)

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Flashback Versions Query Example

SQL> select department_id, department_name, manager_id, 2 versions_starttime, versions_endtime, 3 versions_operation 4 from fv 5 versions between timestamp 6 (systimestamp - interval '5' minute) 7 and (systimestamp) 8 order by department_id, versions_starttime;

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Flashback Versions Query

Dept DeptName MGR_ID VERSIONS_STARTTIME VERSIONS_ENDTIME V

------ ---------------------- ---------- ----------------------------- ---------------------------- - 10 Administration 888 23-FEB-06 05.27.01 PM

U 10 Administration 200 23-FEB-06

05.27.01 PM 20 Marketing 201 30 Purchasing 114 40 Human Resources 203

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Flashback Versions Query

Example

SQL> select versions_xid xid, versions_startscn start_scn, 2 versions_endscn end_scn, versions_operation

oper, 3 department_id, department_name,

manager_id 4 from fv 5 versions between scn 6 minvalue 7 and maxvalue;

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Flashback Version Query

XID START_SCN END_SCN O Dept DeptName MANAGER_ID------------------------ --------------- --------------- - ------- ------------------- -----------------08002400E9080000 5373412 U 30 Purchasing

77706000000DB080000 5373406 U 10 Administration

888 5373406 10 Administration 200 20 Marketing 201 5373412 30 Purchasing 114 40 Human Resources 203

6 rows selected.

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Flashback Transaction Query

View/Recover all data modifications at Transaction level

FLASHBACK_TRANSACTION_QUERY view provides Undo SQL among other information

SELECT ANY TRANSACTION privilege needed to access this view

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Flashback Transaction Query Can be used to audit and analyze

changes

Can assist in testing Application process

Only committed changes can be seen

Supplements Flashback Versions Query

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Flashback Transaction Query FLASHBACK_TRANSACTION_QUERY View Name Null? Type ----------------------------- -------- -------------- XID RAW(8) START_SCN NUMBER START_TIMESTAMP DATE COMMIT_SCN NUMBER COMMIT_TIMESTAMP DATE LOGON_USER VARCHAR2(30) UNDO_CHANGE# NUMBER OPERATION VARCHAR2(32) TABLE_NAME VARCHAR2(256) TABLE_OWNER VARCHAR2(32) ROW_ID VARCHAR2(19) UNDO_SQL VARCHAR2(4000)

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Flashback Transaction Query

Example: List transactions and affected tables in ‘KIRTI’

schema after a certain date and time

SQL> select xid, operation, start_scn, commit_scn 2 table_owner, table_name, logon_user, undo_sql 3 from flashback_transaction_query 4 where table_owner = 'KIRTI' 5 and start_timestamp >= 6 to_timestamp('02/03/06 17:27:00','MM/DD/YY

HH24:MI:SS');

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Flashback Transaction Query

XID OPERATION START_SCN COMMIT_SCN TABLE_OWNER TABLE_NAME ----------------------- --------------- -------------- ----------------- ------------------ -----------------

LOGON_USER ---------------- UNDO_SQL------------------------------------------------------------------------------------------06000000DB080000 UPDATE 5373227 5373406 KIRTI FV

KIRTIupdate "KIRTI"."FV" set "MANAGER_ID" = '200' where ROWID = 'AAANtjAAEAAAAGkAAA';

08002400E9080000 UPDATE 5373406 5373412 KIRTI FT KIRTI

update "KIRTI"."FT" set "MANAGER_ID" = '204' where ROWID = 'AAANtkAAEAAAAGsAAC';

08002400E9080000 UPDATE 5373406 5373412 KIRTI FV KIRTI

update "KIRTI"."FV" set "MANAGER_ID" = '114' where ROWID = 'AAANtjAAEAAAAGkAAC';

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Flashback Database Set entire database to point in

time in the past Similar to the database Point In

Time Recovery Special setup is required to enable

this functionality – Does not use undo segments and Recyclebin

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Flashback Database Flashback Logs - New type of log

files FB Logs are written to by a new

background process RVWR FB Logs are kept in flashback area FB Logs contain before images of

Oracle data blocks and are not archived

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Flashback Database New initialization parameters

DB_RECOVERY_FILE_DEST Default location of flash recovery area

DB_RECOVERY_FILE_DEST_SIZE Hard limit for the disk space used by files

in recovery area DB_FLASHBACK_RETENTION_TARGET

Upper limit in minutes on how far database can be flashed back

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Flashback Database New Views

V$FLASH_RECOVERY_AREA_USAGE Usage information about flash recovery area

V$FLASHBACK_DATABASE_LOG Information about flashback data, used for sizing

flash recovery area V$FLASHBACK_DATABASE_STAT

Information about I/O overhead of logging flashback data, estimated flashback spaces based on workloads

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Flashback Database Set up database for Flashback mode

Define new initialization parameters Mount the database Enable Archive log mode, if required Switch database to run in ‘flashback’

modealter database flashback on;

Open database

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Flashback Database Database can be flashed back using:

SQL commandSQL> flashback database to scn|timestamp;

RMAN command RMAN> flashback database to scn|time;

OEM Recovery Wizard Database must be in ‘mount’ mode Database must be opened with

‘resetlogs’

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Flashback Database Oracle10g R2

Restore points Aliases to SCN that you can use in

flashback database command

create restore point batch_start_1; create restore point batch_mid_1;

flashback database to restore point batch_mid_1;

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Flashback Database Oracle10g R2

Restore points V$RESTORE_POINT shows defined

restore points Remove unwanted restore point drop restore point batch_start_1;

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Questions ?

Thank you.

Contact: KD_U4@yahoo.com