4 Replies Latest reply on Jan 23, 2014 12:39 PM by Karan

    Dataguard redo transmit  from primary to standby

    GTS (DBA)

      Good Morning all ;

       

      When user performs commits. The LGWR reads the redo record from the log buffer  at that  time ,

      The LNS reads the same redo record from the log buffer and transmits it to the standby database using Oracle Net Services.

       

      but oracle official link says .. LOG_ARCHIVE_DEST_n Parameter Attributes

       

      ARCH & LGWR specifies  ,  whether redo transport services use archiver processes (ARCn) or the log writer process (LGWR)

      to collect transaction redo data and  transmit it to standby destinations.


      ---------------------------------


      Many experts are saying LGWR will NOT send any redo to  standby database.


      Please anyone clarify.

        • 1. Re: Dataguard redo transmit  from primary to standby
          JohnWatson

          You are reading the 10.x docs. The ARCH | LGWR attribute no longer exists (except for backward compatibility).

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          • 2. Re: Dataguard redo transmit  from primary to standby
            Karan

            From 11g onwards there is no more overhead on LGWR, Its the LNS who will do it, for performance reasons make sure you have ASYNCH option enabled for archiving in order for oracle not to wait for confirmation of the redo to be written to standby location before committing the record.

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            • 3. Re: Dataguard redo transmit  from primary to standby
              GTS (DBA)

              Hi karan ;


              Thanks for your suggestion. My DB version is 10gr2.


              I think all following four attributes are doing same thing during

              redo transfer from primary to standby ! - Is it really ?


              1) At any sense  affirm and sync work as similar ?

              2) At any sense  noaffirm and async work as similar ?


                - Could you please clarify ?


              GTS - ASIA PACIFIC.

              • 4. Re: Dataguard redo transmit  from primary to standby
                Karan

                In simple words the SYNC will make sure network I/O is done synchronously when using LGWR yes in 10G definately while the NOAFFIRM attribute will make sure that all disk I/O to archived redo log files and standby redo log files is to be performed asynchronously and AFFIRM being the opposite of NOAFFIRM isnt it ...please see in NOAFFIRM that the LGWR process on the primary database does not wait until the disk I/O completes before continuing. When the primary database is in maximum protection mode or maximum availability mode, destinations archiving to standby redo log files and using the log writer process are automatically placed in SYNC mode.

                 

                 

                Below is an example

                 

                 

                LOG_ARCHIVE_DEST_2='SERVICE=sby1 LGWR SYNC AFFIRM'