FORCE LOGGING

I want to create a physical standby database. The primary database is in archive log mode, and the 50% of the data belong to the staging area of datawarehouse. During ETL processes the database generates great amount of GBs of redologs. This tables contain temporary data that are only used for ETL process.
Can I set the database like FORCE LOGGING=N and set FORCE LOGGING=Y only for the tablespace that contain the tables of data (production, not intermediate) ???

If you are trying to run a physical standby, for any database larger and more important than a toy, across the internet you are doomed to failure.
Databases do not fail on predictable schedules.
A DR site means a DR site ... it does not mean someplace out there in the cloud. For all you know your redo is being shipped to the moon and
back. Buy room in a data center no more than 500km away from your current location.
DR is for serious people with serious issues. If you do not need it then don't build it. If you do need it build it correctly.

Similar Messages

Advantage of FORCE LOGGING over NOLOGGING

Hi,
Can you please help me on the advantages of using force logging mode with a standby database and the effect of it in indexes etc. Also, it may help if you could also share ideas on difference between the two modes?
Thanks,
Jennah

<i>>> Can you help me what factors would be sacrificed</i>
This really depends on your system, in most cases you will not be able to see a difference. However i did a small test:
- drop index, restart db
- create index with logging (measure time/redo size)
- drop index, restart db
- create index with logging (measure time/redo size)
Result:
logging - Elapsed: 00:02:40.68 / Redo size: 800mb
nologging - Elapsed: 00:02:20.29 / Redo size: 1.5mb
Here the full test:
[code]SQL> select a.name, b.value from v$statname a, v$mystat b where a.statistic# = b.statistic# and a.name = 'redo size';
NAME                                                                  VALUE
redo size                                                             28304
SQL> CREATE UNIQUE INDEX "SAPR3"."CDCLS~0" ON "SAPR3"."CDCLS"
("MANDANT", "OBJECTCLAS", "OBJECTID", "CHANGENR", "PAGENO")
PCTFREE 10 INITRANS 2 MAXTRANS 255
STORAGE(INITIAL 65536 NEXT 65536 MINEXTENTS 1 MAXEXTENTS 2147483645
PCTINCREASE 0 FREELISTS 1 FREELIST GROUPS 1 BUFFER_POOL DEFAULT)
TABLESPACE "PSAPCLUI" LOGGING;
Index created.
Elapsed: 00:02:40.68
SQL> select a.name, b.value from v$statname a, v$mystat b where a.statistic# = b.statistic# and a.name = 'redo size';
NAME                                                                  VALUE
redo size                                                         834714816
SQL> select segment_name, bytes/1024/1024 "Size_MB" from dba_segments where segment_name = 'CDCLS~0'
SEGMENT_NAME            Size_MB
CDCLS~0                     800
drop index / db restart here
SQL> select a.name, b.value from v$statname a, v$mystat b where a.statistic# = b.statistic# and a.name = 'redo size';
NAME                                                                  VALUE
redo size                                                             28992
SQL> CREATE UNIQUE INDEX "SAPR3"."CDCLS~0" ON "SAPR3"."CDCLS"
("MANDANT", "OBJECTCLAS", "OBJECTID", "CHANGENR", "PAGENO")
PCTFREE 10 INITRANS 2 MAXTRANS 255
STORAGE(INITIAL 65536 NEXT 65536 MINEXTENTS 1 MAXEXTENTS 2147483645
PCTINCREASE 0 FREELISTS 1 FREELIST GROUPS 1 BUFFER_POOL DEFAULT)
TABLESPACE "PSAPCLUI" NOLOGGING;
Index created.
Elapsed: 00:02:20.29
SQL> select a.name, b.value from v$statname a, v$mystat b where a.statistic# = b.statistic# and a.name = 'redo size';
NAME                                                                  VALUE
redo size                                                           1520824
SQL> select segment_name, bytes/1024/1024 "Size_MB" from dba_segments where segment_name = 'CDCLS~0';
SEGMENT_NAME            Size_MB
CDCLS~0                     800[/code]

Force logging in archivelog mode

Hi !!!
What happen if I have "force_logging" parameter set to true when the database is in archivelog mode ?
Thanks.

rarain wrote:
Hi Juamd,
You should only use this option when it is really required because this option will forcibly generate redo for all Nologging operations that means you might find more archives and you need to setup more space for archive.
Normally we use this option when we need to replicate data changes from one database to another database like in standby configuration, Golden Gate replication etc. I would suggest you to monitor Redo amount generated after enabling this option and accordingly estimate archive space and backup space for archive.
Thanks...Ah, don't agree with that at all. You can compromise your recovery if you happen to want to restore to a point-in-time when there was a NOLOGGING operation going on. Fine, if it's an index, but if it happens to be on a table...
(Yes, been there, done that - with a non-Production database, thankfully)
This is one of the 'must haves', IMO, for Production - set it at the database-level and it overrides any tablespace or object setting.
Archivelogs are generated for a reason. If you have a particular operation that really does massively benefit from NOLOGGING and is something you are sure that you simply re-run/re-create yourself, fine. If not, by default, you really should FORCE LOGGING.

Ora-02331 error - while trying to force logging

Hi friends,
i am trying to configure the physical standby database and i am following this documentation http://download.oracle.com/docs/cd/B19306_01/server.102/b14239/create_ps.htm.
when i am trying to do the force logging i am getting the following error.
SQL> alter database force logging;
alter database force logging
ERROR at line 1:
ORA-02231: missing or invalid option to ALTER DATABASE
Can anyone please tell me why it's happening?
Thanks

Which database are you doing this on? Supposed to run
it on the primary. I have only one database i.e primary db and trying to set up physical standby db.
Plus, which version of Oracle? I
see what the document link uses, but that doesn't
mean it is the version you are using.
SQL> select * from v$version;
BANNER
Oracle9i Enterprise Edition Release 9.0.1.1.1 - Production
PL/SQL Release 9.0.1.1.1 - Production
CORE 9.0.1.1.1 Production
TNS for 32-bit Windows: Version 9.0.1.1.0 - Production
NLSRTL Version 9.0.1.1.1 - Production
Can you pls guide me the right way to proceed furthur.

Direct Path Loads Vs FORCED LOGGING

Hello everyone,
I just got below doubt.
Suppose, we've
One Oracle Primary Database (running in FORCED LOGGING mode) and,
One Oracle Standy Database (Oracle Data Gaurd)
My doubt is that if we use sqlloader direct path to load data in a table in primary database, will it generate/send the redo and ship the same to standby database ?

Thanks Anil,
But have a doubt again.
How does direct path data upload generate redo if it's working on just data blocks.
I.e. get the block adjust the high water and put the records.

Sql query needed to verify force logging

Hi.
Does anyone out there have SQL query we need to run in order to see if our db is working in force logging mode?
Thanks.
DA

The FORCE_LOGGING column of v$database view can be queried to verify that the database is in FORCE LOGGING mode. Similarly, the FORCE_LOGGING column of dba_tablespace view provides the same information for each tablespace.
Kamran Agayev A. (10g OCP)
http://kamranagayev.wordpress.com

Physical standby without ALTER DATABASE FORCE LOGGING

Hi,
Is it possible to use physical standby database without executing ALTER DATABASE FORCE LOGGING on primary side?
Can I use alter tablespace force logginng instead?
I want to have one tablespace with nologging option turned on to reduce redo traffic for some operations.
I can not check this because I don`t have enough servers to build standby configuration.

YuriAP wrote:
Hi,
Is it possible to use physical standby database without executing ALTER DATABASE FORCE LOGGING on primary side?
YES
Can I use alter tablespace force logginng instead?
YES
ALTER TABLESPACE <tablespace name> FORCE LOGGING;
I want to have one tablespace with nologging option turned on to reduce redo traffic for some operations.
I can not check this because I don`t have enough servers to build standby configuration.http://download.oracle.com/docs/cd/B10500_01/server.920/a96521/create.htm#1022863

Force logging at tablespace level for standby database

Hi
Can we create a standby database by enabling force logging at tablespace level instead of enabling it at database level.I want to out the tablespace containing indexes in nologging mode so that when I rebuild the indexes no logs will be generated.

Technically, you can create a Standby without having set FORCELOGGING at the Primary database.
You can also then selectively FORCELOGGING for all your important tablespaces (beginning with SYSTEM, SYSAUX, UNDO ....)
However, for a Physical Standby Redo Apply will mark the blocks (e.g. those populated by the CREATE INDEX .. NOLOGGING) as "corrupt". You will get Read Errors (ORA-1578 and ORA-26040) when you attempt to read the index (e.g. for a Table query).
So you have to monitor your NOLOGGING operations and the datafiles where NOLOGGING is applied. You can take Incremental RMAN Backups of such datafiles and restore them to the Standby immediately after the NOLOGGING operations.
Hemant K Chitale

Not dose Force logging.

Hi,
i am trying to create physical standby database.while giving command 'ALTER DATABASE FORCE LOGGING' it gives error like missing or invalid option to alter database.
Pls help.

Hi,
Pls find the output.
SQL> select * from v$version;
BANNER
Oracle9i Enterprise Edition Release 9.0.1.1.1 - Production
PL/SQL Release 9.0.1.1.1 - Production
CORE 9.0.1.1.1 Production
TNS for 32-bit Windows: Version 9.0.1.1.0 - Production
NLSRTL Version 9.0.1.1.1 - Production
SQL> alter database force logging;
alter database force logging
ERROR at line 1:
ORA-02231: missing or invalid option to ALTER DATABASE
SQL>

What is 'force logging'?

Why we need some ddl not to be wroten to the redo logs? What is the idea? How can we recover the database if some infromation in archivelogs is missed?
Thanks in advance

In theory, yo may wish to allow an application to load data as a "no logging" operation, this can speed up large data loads and reduce the volume of archivelogs produced.
However the major drawbacks are:
if you need to recover the database form a backup any data added using a no logging operation performed after the backup was taken will not be recoverable from the archive logs.
If you are using log shipping/data guard these operations will not get transmitted to the standby server.
If you work in a controlled an disciplined enviroment then it should be possible to repeat any no logging operations after the database is recovered as everyone should be aware of the limitations of loading data in this manner.
If you work anywhere thats like the places I've come accross a more likely situation is after a database recovery someone will want to know why data is missing from the database and how long it will be untill you resolve the problem. Usually I set force logging on and let the users think they have the option to run nologgign operations as it leads to a quieter life in the long run.

ALTER DATABSE FORCE LOGGING

hi,
while creating standby database why should we start the database in force logging mode? what the use of it? what does it do?
With Regards
Boo

Synchorinization between primary and secondary database is done through archive logs. It would be safe to force primary database to log everything, so that it reflects to secondary database. That is the reason we have to force logging.

Force logging for data guard

It is my understanding new to version 11g force logging is not required on the database? So we could setup a tablespace for staging tables in no logging and not generate as much redo to be shipped over to the standby?
Is this true or was that feature added in 10? I have hunted around on OTN for some info on the subject. could anyone provide a link?
Thanks

I've seen nothing that indicates "force logging is not required but the idea that somehow there is an advantage to no logging is grossly overstated.
I'd suggest that you go to http://asktom.oracle.com and read Tom's comments about it.
If your system is so close to falling over that a little bit of logging is going to tip it over you've huge problems you'd best deal with immediately.
Consider, for example, setting up your staging tables as global temporary tables.

FORCE LOGGING disabled automatically?

Hi,
This is just strange that on a couple of my 11.2.0.3 dataguard environments on Oracle Linux 6 (64 bit) was found FORCE LOGGING disabled and I just enabled them. Now DBA team remembers correctly that FORCE LOGGING is always enabled while configuring the dataguard. I would like to have opinion from someone if he/she has this kind of scenario with him/her. Is there any way that FORCE LOGGING could get disabled automatically? We never re-created controlfile on primary or standby, but, we have switchover/failover scenarios which are not supposed to disturb FORCE LOGGING?
Or did we really forget to enable FORCE LOGGING?
Salman
<Moderator Edit - deleted link spam - pl see FAQ on where to include signature links - abuse reported to Admins>

Hi Salman,
Can you check the database alert log from the time when it was enabled first time.
Alert log will have completed information on what and when any command was run to disable it.
HTH,
Pradeep

ORA-02231 error when issue ALTER DATABASE FORCE LOGGING

Hi,
Does everybody know why I faced ORA-02231 when issue below command in oracle,
SQL> ALTER DATABASE FORCE LOGGING;
ALTER DATABASE FORCE LOGGING
ERROR at line 1:
ORA-02231: missing or invalid option to ALTER DATABASE
SQL> ALTER DATABASE FORCE LOGGING ;
ALTER DATABASE FORCE LOGGING
ERROR at line 1:
ORA-02231: missing or invalid option to ALTER DATABASE
SQL> ALTER DATABASE FORCE LOGGING
2
SQL> ALTER TABLESPACE BIIS FORCE LOGGING
2 ;
ALTER TABLESPACE BIIS FORCE LOGGING
ERROR at line 1:
ORA-02142: missing or invalid ALTER TABLESPACE option
I use this oracle version:
Oracle9i Enterprise Edition Release 9.0.1.1.1 - Production
PL/SQL Release 9.0.1.1.1 - Production
CORE 9.0.1.1.1 Production
TNS for 32-bit Windows: Version 9.0.1.1.0 - Production
NLSRTL Version 9.0.1.1.1 - Production
Thanks.

Hi Jaffar,
After I checked that you are correct.
I can issue the command without problem in oracle 9i Rel.2.
Thanks for your information.
Tarman.

Direct load with Force Logging enable

Hi All,
I have a dataguard environment with one physical standby database, I have to load a big flat file with close to 50Millions records using sqlldr. can i use direct=true in sqlldr,with force logging enabled on primary? or they is any other way to load this file
FYI- ORACLE 11GR2
Thanks

Thanks for that information.
The direct=true means what you think, Loaded data will not be replicated. However its make sense and your test proves that Data Guard overrides this.
based on this you might as well go conventional path.
Does this help?
Its makes sense that Data Guard would override this, otherwise Data Guard would (or Forced logging) would not be doing its job.
From Oracle doc A96524-01 Database Concepts 19 Direct-Path INSERT
If the database or tablespace is in FORCE LOGGING mode, then direct path INSERT always logs, regardless of the logging or nologging setting.
I know this an older doc, but its unlikely this would have changed

FORCE LOGGING

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