6 Replies Latest reply: Nov 15, 2012 11:39 AM by vlethakula RSS

    General Question for Learning

    927578
      Hi,

      Can anyone pls explain me.. When DBWR writes the data from DB Buffer Cache to Data Files ? what i'm thinking is if user COMMIT the transaction. is this right ? Pls Correct me if i'm wrong if possible pls explain me...
        • 1. Re: General Question for Learning
          sb92075
          924575 wrote:
          Hi,

          Can anyone pls explain me.. When DBWR writes the data from DB Buffer Cache to Data Files ? what i'm thinking is if user COMMIT the transaction. is this right ? Pls Correct me if i'm wrong if possible pls explain me..
          what happens when session does DML that exceeds total RAM?

          when does datafile get changed?
          • 2. Re: General Question for Learning
            927578
            sb92075 wrote:
            924575 wrote:
            Hi,

            Can anyone pls explain me.. When DBWR writes the data from DB Buffer Cache to Data Files ? what i'm thinking is if user COMMIT the transaction. is this right ? Pls Correct me if i'm wrong if possible pls explain me..
            what happens when session does DML that exceeds total RAM?

            when does datafile get changed?
            Thanks for your question also ;).

            Can anyone pls answer this 3 question ? so that we can learn ?
            • 3. Re: General Question for Learning
              Pavan Kumar
              Hi,

              Please refer to Oracle docs
              http://docs.oracle.com/cd/E14072_01/server.112/e10713/process.htm#CNCPT1250
              http://docs.oracle.com/cd/E14072_01/server.112/e10820/bgprocesses.htm

              HTH

              - Pavan Kumar N
              • 4. Re: General Question for Learning
                jgarry
                You might find this informative, especially if you try it yourself: http://arup.blogspot.com/2010/12/100-things-you-probably-didnt-know.html
                • 5. Re: General Question for Learning
                  vlethakula
                  Your datafiles can contain uncomiited and commited data.

                  When you issue a commit, message COMMIT COMPLETE would be displayed that means those changes are written to redolog files from log buffer cache(you are safe these changes are written from memory to files. As files are permanent storage)
                  it is not necessary that those changes are written by dbwr from block buffer cache to datafiles;

                  DBWR is lazy process ,it invokes
                  upon checkpoint
                  buffer cahce needs space
                  • 6. Re: General Question for Learning
                    927578
                    vlethakula wrote:
                    Your datafiles can contain uncomiited and commited data.

                    When you issue a commit, message COMMIT COMPLETE would be displayed that means those changes are written to redolog files from log buffer cache(you are safe these changes are written from memory to files. As files are permanent storage)
                    it is not necessary that those changes are written by dbwr from block buffer cache to datafiles;

                    DBWR is lazy process ,it invokes
                    upon checkpoint
                    buffer cahce needs space
                    Thank you vlethakula