Estimate of Flashback logs to expect for my database

Hi all,
Please I need to know (roughly) the size of flahback logs to expect for my database.
My database is about 500G in size, grows at about 1% per month and I hope to keep flashback logs for 48 hrs.
If you currently use the flashback technology, let me know your database size, how many hours of flashback logs you keep and the size of your logs. If I get 2 or 3 responses, then I'll be able to make an intelligent guess for what my database flahback log size might be.
Regards
baffy

The value of the DB_FLASHBACK_RETENTION_TARGET parameter (1440
minutes in our example) determines how much flashback data the database should
retain in the form of flashback database logs in the flash recovery area. In order to
estimate the space you need to add to your flash recovery area for accommodating
the flashback database logs, first run the database for a while with the flashback
database feature turned on. Then run the following query:
SQL> select estimated_flashback_size, retention_target,
flashback_size from v$flashback_database_log;
ESTIMATED_FLASHBACK_SIZE RETENTION_TARGET FLASHBACK_SIZE
126418944 1440 152600576

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Re: 11g block recover doesn't look for flashback logs
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Hi,
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http://download-uk.oracle.com/docs/cd/B19306_01/server.102/b14200/statements_3001.htm#CJAHHIBI
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Hi,
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RFS IDLE 0 0 0 0
RFS IDLE 0 0 0 0
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Sat Mar 17 04:51:00 2012
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<smacking forehead on the table>
Bloody hell! How the heck I missed that darn "B" ? I guess, time to get some sleep and after that some coffee.Please don't do ;-)
When knowledge is in extreme level, there is possibilities to miss small and small things some time.
@OP,
Here some practice
sys@ORCL> show parameter db_reco
NAME                                 TYPE        VALUE
db_recovery_file_dest                string      C:\Oracle\flash_recovery_area
db_recovery_file_dest_size           big integer 3852M
sys@ORCL> alter system set db_recovery_file_dest_size=3900mb scope=both;
alter system set db_recovery_file_dest_size=3900mb scope=both
ERROR at line 1:
ORA-02065: illegal option for ALTER SYSTEM
sys@ORCL> alter system set db_recovery_file_dest_size=4gb scope=both;
alter system set db_recovery_file_dest_size=4gb scope=both
ERROR at line 1:
ORA-02065: illegal option for ALTER SYSTEM
sys@ORCL> alter system set db_recovery_file_dest_size=3900m scope=both;
System altered.
sys@ORCL> alter system set db_recovery_file_dest_size=4g scope=both;
System altered.
sys@ORCL> show parameter db_reco
NAME                                 TYPE        VALUE
db_recovery_file_dest                string      C:\Oracle\flash_recovery_area
db_recovery_file_dest_size           big integer 4G
sys@ORCL>

Oracle not using space occupied by flashback logs

Hi,
oracle 10g R2 10.2.0.1 on RHEL 4 64-bits.
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Others have reported similar issues: http://www.wayneadamsconsulting.com/
>
One thing that I have not seen the database do, however, is delete reclaimable flashback logs in order to make room for a backup. If there is not enough free space in you FRA for a backup but there is plenty of space used by relcaimable flashback logs, RMAN and the database will not delete flashback logs to free up room in the FRA for the backup. This seems like a fairly large gap in the flashback log functionality, but hopefully Oracle will handle it in a future release.
>
See MOS note: Space issue in Flash Recovery Area( FRA ) [ID 829755.1] .
Note also that 10.2.0.1 is a old 10.2 release and that you could consider upgrading to 10.2.0.4.

Remove the flashback logs in EBS envoirnment.

Hi,
In my production database(primary) machine flashback is ON.
So, logs are creating in following directory:
/d01/silprod/SILP/db/apps_st/data/archives/SILP01_SER/flashback
In my physical standby database flashback is OFF.
So, My question is that:
Can I remove the flashback logs from production safely?
Thanks.

Hi,
How to identified that which archive logs no longer needed and can delete, and how to reclaim the archive space?
Is below steps are correct?
Archive location: /d01/silprod/SILP/db/apps_st/data/archives/SILP01_SER/archivelog
Archive files name like: o1_mf_1_894_5jpkly8k_.arc -------------> Sequence#=894
Archive Size occupied:
> du -sh archivelog/ ------------> 2.7G archivelog/
STEP#1:
SQL> SELECT THREAD#, SEQUENCE# FROM V$LOG WHERE STATUS='CURRENT'; -----------> RESULT: THREAD#=1 AND SEQ$= 894
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SQL> SELECT THREAD#, SEQUENCE# FROM V$LOG WHERE STATUS='CURRENT'; -----------> RESULT: THREAD#=1 AND SEQ$= 895
Confirm the current file have been applied to the standby database with the below query
SQL> SELECT MAX(SEQUENCE#) FROM V$LOG_HISTORY; -----------------> RESULT: THREAD#=1 AND SEQ$= 894
Step#2:(Memory)
> delete unwanted archive log files from disk (rm, del commands)---------> all archives files deleted expected of PROD_1_894.arc
RMAN> crosscheck archivelog all; - marks the controlfile that the archives have been deleted
RMAN> delete expired archivelog all; - deletes the log entries identified above.
But, How to identified that which flashback files no longer needed and can delete, and how to reclaim the flashback space?
Flashback location: /d01/silprod/SILP/db/apps_st/data/archives/SILP01_SER/flashback
Flashback files name like: o1_mf_5jlc8gb0_.flb, o1_mf_5jlcb2bv_.flb etc ------------> how to identified which file(File Name has no sequence#) should I delete?
Flashback Size occupied:
> du -sh flashback/ ------------> 3.5G flashback/

Delete flashback log dynamically.

i want to delete flashback log dynamically.
suppose today is 1st feb while running shell script it will remove flashback log 31stjan ...
i have set retention policy 1 days.
following is the my sh script
=====================
#!/bin/sh
# Daily Backup
. oraenv.oratest
export NLS_DATE_FORMAT="Dy DD-Mon-YYYY HH24:MI:SS"
LOG_DIR="/var/log/oracle"
LOG_FILE="$LOG_DIR/$ORACLE_SID-daily-backup.log"
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pushd $HOME/rman
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echo -e "\n***\n*** BACKUP FAILURE: Database $ORACLE_SID on $HOSTNAME \n***"
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EOF
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popd
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run {
# Remove any obsolete files prior to backup
crosscheck backupset;
crosscheck copy;
delete noprompt obsolete;
delete noprompt expired backup;
delete noprompt expired copy;
# Incremental backup and update of current image copy
allocate channel oem_disk_backup device type disk;
recover copy of database with tag 'ORA\$OEM_LEVEL_0';
delete noprompt obsolete;
delete noprompt expired backup;
delete noprompt expired copy;
backup incremental level 1 cumulative copies=1 for recover of copy with tag 'ORA\$OEM_LEVEL_0' database;
# Following backup - remove any now-obsolete files
delete noprompt obsolete;
delete noprompt expired backup;
delete noprompt expired copy;

RMAN cannot delete flashback logs, these are maintained automatically according to parameter 'db_flashback_retention_target'. Don't confuse FLASHBACK DATABASE with RMAN point-in-time recovery.
RMAN backups become obsolete as soon as no longer needed to meet the defined retention policy, 'delete obsolete' will never delete flashback logs.

Flashback Logs Location

Well, I am confused whether Oracle Flashback Technology uses Undo Tablespace or Flash Recovery Area. I was going through http://www.oracle.com/technology/deploy/availability/htdocs/Flashback_Overview.htm, and the page mentions both Undo Tablespace and Flash Recovery Area.
Can someone please clarify.
Thanks

furqan_sindhu wrote:
Well, I am confused whether Oracle Flashback Technology uses Undo Tablespace or Flash Recovery Area. Completely wrong thought process. Oracle Flashback Technology is based on the Undo data which is stored Undo Tablespace. The Flash Recovery Area is nothing but a destination where the Flashback Logs are stored but they are used for a different purpose, which is for sending the complete database back into the past. So comparing both Flashback and FRA is actually a wrong thing to do.
I was going through http://www.oracle.com/technology/deploy/availability/htdocs/Flashback_Overview.htm, and the page mentions both Undo >Tablespace and Flash Recovery Area.
Read my reply above. Flashback is based on the Undo data which is not stored in the FRA but in the Undo tablespace. The FRA is used to store the backup files, archive files and a sepcial set of files called flashback logs (which I mentioned above) . Don't compare both and a suggestion, don't read white papers since they contain snippets of information only. Read oracle docs since they contain the complete stuff.
HTH
Aman....

During EXPDP .flb (Flashback logs) generation is very High

hi,
my database is in flashback log mode and i created a gurented restore point to take back my DB to restore point..in this status i start logical backup by EXPDP of a schema and during expdp lot of .flb logs were generated..
what is the concern of this EXPDP with the huge generation of .flb log ...plz guide
DB Version is 10g(10.2.0.4)
regards,

Hi,
As per my undestanding,
1) Datapump uses "flashback query."
2)Flashback query does not use flashback logs. It uses UNDO.
3)Flashback Query uses Oracle's multiversion read-consistency capabilities to restore data by applying undo as needed. Oracle Database 10g automatically tunes a parameter called the undo retention period. The undo retention period indicates the amount of time that must pass before old undo information—that is, undo information for committed transactions—can be overwritten. The database collects usage statistics and tunes the undo retention period based on these statistics and on undo tablespace size
Your expdp job has nothing to do with flashback log.
Best regards,
Rafi.
http://rafioracledba.blogspot.com

Excessive flashback log generates with select statement

Hi everyone;
We have some extractions taken from a "flashback on" database.
Extractions are just select statements but when they are run, database produces excessive flashback logs.
What may be the reason database produce flashback logs with just select statements?
(It's certain that there are no insert-update-delete operations)
Version: 10.2.0.4.3
Thanks...

Do you do heavy update/delete before you select the statements ?
I am not very sure if delayed block cleanout also have the same effect on flashback logs but the output below is leading me to think that way
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BEGIN_TIME        END_TIME          FLASHBACK_DATA    DB_DATA REDO_DATA ESTIMATED_FLASHBACK_SIZE
20100527 15:32:53 20100527 15:50:16      875266048 1207132160 2038729728                        0
20100527 14:32:50 20100527 15:32:53      248160256 127295488 450139648               1.3215E+10
20100527 13:32:48 20100527 14:32:50       10452992   15646720    4400640               1.5549E+10
20100527 12:32:43 20100527 13:32:48      745693184 948461568 1311620608               2.2789E+10
20100527 11:25:56 20100527 12:32:43     1262026752 1984741376 2358546432               2.7212E+10
HR@ORACOS> set autotrace traceonly statistics
HR@ORACOS> update base_table_np set y='INVALID';
commit;
4021808 rows updated.
Statistics
       2512 recursive calls
    8341430 db block gets
    4069140 consistent gets
     120569 physical reads
1908471980 redo size
        848 bytes sent via SQL*Net to client
        793 bytes received via SQL*Net from client
          3 SQL*Net roundtrips to/from client
          1 sorts (memory)
          0 sorts (disk)
    4021808 rows processed
HR@ORACOS> set autotrace off;
HR@ORACOS> select * from v$flashback_database_stat;
HR@ORACOS>
BEGIN_TIME        END_TIME          FLASHBACK_DATA    DB_DATA REDO_DATA ESTIMATED_FLASHBACK_SIZE
20100527 15:32:53 20100527 16:00:36     1236664320 2021974016 4019910656                        0
20100527 14:32:50 20100527 15:32:53      248160256 127295488 450139648               1.3215E+10
20100527 13:32:48 20100527 14:32:50       10452992   15646720    4400640               1.5549E+10
20100527 12:32:43 20100527 13:32:48      745693184 948461568 1311620608               2.2789E+10
20100527 11:25:56 20100527 12:32:43     1262026752 1984741376 2358546432               2.7212E+10
HR@ORACOS> set autotrace traceonly statistics
HR@ORACOS> select * from base_table_np;
4021808 rows selected.
Statistics
        139 recursive calls
          0 db block gets
      53908 consistent gets
       4404 physical reads
    1652384 redo size                                                  ------->delayed block cleanout effect
175008833 bytes sent via SQL*Net to client
      88996 bytes received via SQL*Net from client
       8045 SQL*Net roundtrips to/from client
          4 sorts (memory)
          0 sorts (disk)
    4021808 rows processed
HR@ORACOS> set autotrace off
HR@ORACOS> select * from v$flashback_database_stat;    ----flashback data size increases
HR@ORACOS>
BEGIN_TIME        END_TIME          FLASHBACK_DATA    DB_DATA REDO_DATA ESTIMATED_FLASHBACK_SIZE
20100527 15:32:53 20100527 16:01:11     1305264128 2054594560 4021728256                        0
20100527 14:32:50 20100527 15:32:53      248160256 127295488 450139648               1.3215E+10
20100527 13:32:48 20100527 14:32:50       10452992   15646720    4400640               1.5549E+10
20100527 12:32:43 20100527 13:32:48      745693184 948461568 1311620608               2.2789E+10
20100527 11:25:56 20100527 12:32:43     1262026752 1984741376 2358546432               2.7212E+10Basically what I do is I update a 4 million table big redo generated with flashback logs
When I do select after the update I still see the redo generated because of delayed block cleanout but what I also see is the slight increase in flashback data size (check the first row of flashback_database_stat) which suits what you asking for. Select statement generates flashback log
Tested on 11.2.0.1 with single active session on the db
Coskan Gundogar
Blog: http://coskan.wordpress.com
Twitter: http://www.twitter.com/coskan
Linkedin: http://uk.linkedin.com/in/coskan
---------

Flashback log purge

Hi
I`ve set db_recovery_file_dest_size to 20m and flashback retention target to 60mins.
As far as I know flashback logs are automatically deleted when the fra is filled up.
I notice that there are 4 flashback logs and they are never deleted in the last two days.
What is the reason for that ?
log_1.287.760141739
log_2.281.759973635
log_2.285.760141745
log_3.298.760145161

It only possible it will reuse it.
Most of the time it will create a new log from my experience.
It all depends on your settings.
I watch v$flash_recovery_area_usage fairly close on my systems and the flashback logs are a fairly small piece of my FRA.
Archive and RMAN backups use up most of the space. For the most part I let Oracle just handle the flashback logs.
Best Regards
mseberg
Query I like for this :
SELECT
ROUND((A.SPACE_LIMIT / 1024 / 1024 / 1024), 2) AS FLASH_IN_GB,
ROUND((A.SPACE_USED / 1024 / 1024 / 1024), 2) AS FLASH_USED_IN_GB,
ROUND((A.SPACE_RECLAIMABLE / 1024 / 1024 / 1024), 2) AS FLASH_RECLAIMABLE_GB,
SUM(B.PERCENT_SPACE_USED) AS PERCENT_OF_SPACE_USED
FROM
V$RECOVERY_FILE_DEST A,
V$FLASH_RECOVERY_AREA_USAGE B
GROUP BY
SPACE_LIMIT,
SPACE_USED ,
SPACE_RECLAIMABLE ;And
column FILE_TYPE format a20
select * from v$flash_recovery_area_usage;Edited by: mseberg on Aug 24, 2011 9:01 PM

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Estimate of Flashback logs to expect for my database

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