4 Replies Latest reply: Mar 27, 2013 3:22 PM by Orna Weisman RSS

    What is "Parallel" in the parallel apply

    Orna Weisman
      Hi

      How exactly is Oracle utilizes the parallel apply processes in a physical standby ?
      Per my understanding , an apply is always sequential , log by log.

      what is being parallelized in the apply processes in a 11.2 physical dataguard ?

      Thanks
      Orna
        • 1. Re: What is "Parallel" in the parallel apply
          mseberg
          Hello;

          Not much information on this.


          The ApplyParallel configurable database property specifies whether Redo Apply should use multiple processes to apply redo data to the physical standby database.


          Source - Oracle® Data Guard Broker 11g Release 2 (11.2) Part Number E17023-08

          So the way I read it, it just multiple processes

          Kind of a vague note here too :

          http://www.oracle.com/technetwork/database/features/availability/maa-wp-10grecoverybestpractices-129577.pdf


          Update

          Tiny bit more here :

          http://www.stanford.edu/dept/itss/docs/oracle/10g/server.101/b10822/dbresource.htm#i1029542

          Emre Baransel site

          http://emrebaransel.blogspot.com/2008/11/dataguard-performance.html


          Best Regards

          mseberg

          Edited by: mseberg on Mar 27, 2013 1:51 PM

          Edited by: mseberg on Mar 27, 2013 2:37 PM
          • 2. Re: What is "Parallel" in the parallel apply
            Orna Weisman
            Vague indeed :-)

            I wonder if this is even fully disclosed anywhere .
            I could not find any good explanation
            • 3. Re: What is "Parallel" in the parallel apply
              Levi Pereira
              I believe it's the same concept of Parallel Recovery

              Not using Parallel Recovery
              This single process will read the archived logs and determine which changes are required for the specific data files being recovered. The data block is read into the buffer cache, and the
              redo is applied to it. Each time an archived log is completely applied, a media recovery checkpoint occurs which signals DBWR to write all the dirty blocks in the buffer cache to the data files.

              Using Parallel Recovery
              The process that issues the recovery command reads the archived logs as before, but instead of reading the blocks in the cache and applying the redo to them directly, it passes that work to the parallel execution slave processes. To make sure the redo is applied to the data files in SCN order, the parallel slaves work on different ranges of data blocks, so
              they will not interfere with each other, and also the redo will still get applied in SCN order for each data block.

              Read it:
              http://www.oracle.com/technetwork/database/features/availability/br-optimization-132612.pdf