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8 Replies Latest reply: Nov 2, 2012 3:45 AM by UweHesse RSS

Physical standby in archive log mode

User448413-OC Newbie
Currently Being Moderated
HI ,

Our phyiscal standby database is running in archive log mode,

1.Is it manadatory to have it in archive log mode ?

2.As it is in archive log mode , does it produce any archivelog ?
  • 1. Re: Physical standby in archive log mode
    mseberg Guru
    Currently Being Moderated
    Hello;
    1.Is it manadatory to have it in archive log mode ?
    Yes.
    2.As it is in archive log mode , does it produce any archivelog ?
    Only if you switch the its role to Primary.

    Thinking of the Primary and Standby database as one database is different roles.
     SELECT DATABASE_ROLE  FROM V$DATABASE;
    In the "PRIMARY" role it must produce archive. Otherwise Data Guard cannot and would not work correctly if you do a switchover or failover.


    Please consider closing you question if answered.


    Best Regards

    mseberg
  • 2. Re: Physical standby in archive log mode
    User448413-OC Newbie
    Currently Being Moderated
    Why it is manadatory to enable archive log in standby ,Ofcourse we can enable explicitly while performing failover/switchover ?

    Why does it need to produce archive in standby role?
  • 3. Re: Physical standby in archive log mode
    mseberg Guru
    Currently Being Moderated
    Hello again;

    The Standby is a clone of the Primary. I assume we are talking Physical Standby.
    Why does it need to produce archive in standby role?
    Its does not produce archive in the Standby role. I have seen a Standby produce a log now and then, but not log after log like a primary. A Standby database does not write Redo or use Redo logs, it uses Standby Redo logs. Since Redo logs are not used, archive is not written.
    Why it is manadatory to enable archive log in standby?
    Smart design I'm thinking. Why would Oracle make us add this complex step to a failover/switchover?

    Keep it simple if possible.

    Data Guard Concepts and Administration 11g Release 2 (11.2) E10700-02

    Database Concepts

    http://docs.oracle.com/cd/E11882_01/server.112/e25789/process.htm


    Best Regards

    mseberg
  • 4. Re: Physical standby in archive log mode
    User448413-OC Newbie
    Currently Being Moderated
    Then . my question would be

    " Still it is in archve log mode , but not producing archive logs ? How?

    Thanks,
    Uday
  • 5. Re: Physical standby in archive log mode
    saurabh Pro
    Currently Being Moderated
    the reason for standby database not producing archive log is that it is not opened it is in mount stage. In this you cannot perform any operation to cahange tha data in the database so it is not producing archive log.
  • 6. Re: Physical standby in archive log mode
    JohnWatson Guru
    Currently Being Moderated
    Of coutrse it is producing archive logs. What do you think it does when a standby log fills?
  • 7. Re: Physical standby in archive log mode
    mseberg Guru
    Currently Being Moderated
    John;

    With all due respect this answer is very misleading. A Standby database does not produce archive logs. It receives redo data from a Primary database.

    Your answer makes seem like the Standby is writing its own logs.

    The Standby is not "producing archive logs", writing a copy of the Primary's archive and producing archive are two different things.

    Best Regards

    mseberg
  • 8. Re: Physical standby in archive log mode
    UweHesse Expert
    Currently Being Moderated
    A Physical Standby will always create respectively get the same Archive Logs as the Primary.
    They are used for Redo Apply - when Real-Time Apply can't (always) be done - there and they are mandatory.

    A strategy to get rid of those (applied) Archive Logs is required, but you cannot (and don't want to) switch that off.

    Technically speaking, the Standby really creates Archive Logs - when a Standby Log was filled up by the RFS, an ARCH process on the Standby creates an Archive Log.
    Only when Archive Log Gap resolution takes place, an ARCH from the Primary will ship an Archive Log to the Standby.

    A special case would be Logical Standby, where additionally to the above also Online Logs fill up and get archived.

    Kind regards
    Uwe Hesse

    "Don't believe it, test it!"
    http://uhesse.com

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