Standby Database
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Thread: Standby Database

  1. #1
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    Aug 2000
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    We are setting up a standby db - we're doing a fresh install of Oracle on the box first - should we enable archiving for the standby db? Thx.

  2. #2
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    you don't have to since standby box in recovery mode but it will be extra step when you turn standby box on

  3. #3
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    Oracle suggests that the init.ora parameters for both the primary and standby db be identical as far as possible. So I think the answer would be yes. Or is my thinking wrong ?? :-)

    -amar

  4. #4
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    amar,

    Yes. They should be identical. You cannot apply redo logs to any database not in ARCHIVELOG mode, so standby database won't even work without this setup. Even if you could, who would go through the effort/expense to develop a standby database only to have a disaster requiring the backup, then run that backup in NOARCHIVELOG mode?


  5. #5
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    I don't think it is mandatory to have the stand by in archive log mode.

  6. #6
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    I am interested in knowing how to create the standby db in NO-ARCHIVELOG mode. Somebody mind englightening me how to do it ?? :-)

    -amar

  7. #7
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    gsprince,

    I reviewed numerous Metalink articles and Oracle documentation to research this thread. I could not find anything that indicated directly that NOARCHIVELOG is not available when operating a standby DB. I would think that it would have been in the Metalink articles, because they did specifically mention that the Primary database must be in ARCHIVELOG mode (obviously). However, those same articles also stated that it was imperative to make the primary and standby as close to identical as possible, and they said to copy the primary init.ora for use on the standby, and then specified exactly which parameters to change for proper standby functionality. None of the parameters to be changed involved setting ARCHIVELOG mode.

    So, barring any further discoveries (I'll look around some more), I cannot substantiate my earlier post that ARCHIVELOG mode is mandatory. Since I'm aware that under "normal" circumstances, redo logs cannot be applied except to a database in ARCHIVELOG mode, it makes sense to me that the same restriction would apply here. However, I can also see that someone may wish to use the standby for reporting, analysis or some other read-only mode rather than production. Thus ARCHIVELOG mode might not even be relevant or useful to their operation and it would make sense to allow the DBA to decide the appropriate mode of operation of the standby DB.

    Anyone have a definitive answer?

  8. #8
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    Don't consider this as a definitive answer, as I don't have any standby configuration handy to prove/test my thoughts.

    Archivelog mode is written in the controlfile. You can't create standby database file on the primary instance if it is not running in archivelog mode, so initially your standby database will be mounted in archive log mode in any case. You also can't change the mode from archivelog to noarchivelog while your database needs media recovery. In standby database the system assumes the database constantly needs media recovery (you have to specify STANDBY while mounting the database), so I guess it will never allow you to change the mode from archivelog to noarchivelog. So you are bound to archivelog mode with standby database, you can't change that. But even if you could set it to noarchive log I can't see any advatage of running standby in noarchivelog. Neither during recovery nor during database being opened in readonly mode no redologs will be generated, so archiver won't have to do anything and will not use any system resources at all.

    Another comment on this statement from one of the previous posts in this thread: "You cannot apply redo logs to any database not in ARCHIVELOG mode". This is simply not true. If you switch your database from archivelog to noarchivelog mode you can still perform a media recovery using archived redologs from the time when the database was in archivelog mode.
    Jurij Modic
    ASCII a stupid question, get a stupid ANSI
    24 hours in a day .... 24 beer in a case .... coincidence?

  9. #9
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    Aug 2000
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    FYI: an update.

    I posted this question on Metalink's Oracle server forum, an an Oracle Corp. tech person replied:

    Can I run a STANDBY database in NOARCHIVELOG mode?



    yes. actually, standby is the mode that the database is in.
    So views lik v$archived_log are for a different purpose on
    a standby.

    Regards,
    Rowena Serna
    Oracle Corporation


  10. #10
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    Although the answer from Oracle Support representative is somewhat confusing ("yes. actually, *standby* is the mode that the database is in" - asterisks added by J.M.), the question is what they actually ment, even if they thought *noarchivelog* instead of *standby*.

    How can we determine in which archiving mode the instance is running? One option would be to isue "ARCHIVE LOG LIST" in svrmgrl or in SQL*PLus, or to "SELECT log_mode FROM v$database;". So if someone have standby configuration handy it would be nice to post the results from the above commands on the standby database. I would be surprised if they would report standby to be in noarchivelog mode! If it realy is running in noarchivelog, what happens when you convert standby to "normal" database mode? Does it automatically swith to archivelog (because I'm positive the converted database runs in archivelog mode, just like previous primary did)?

    What I suspect the Oracle Support representative realy ment was: standby database is *efectively* running in noarchivelog mode, although it formaly is configured as archivelog. The ARCx process is just sitting there, doing nothing, just like in the normal database in noarchive mode.
    Jurij Modic
    ASCII a stupid question, get a stupid ANSI
    24 hours in a day .... 24 beer in a case .... coincidence?

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