10 Replies Latest reply: Mar 5, 2013 9:31 PM by Dude! RSS

    Doubt regarding redo log group

    sandy121
      I want to drop a particular redo log group , but even after multiple log switches, it's status is either 'Active' or 'Current' , do I have any other better approach to make the status of that particular group 'inactive' rather than continuing the log switching processes in intervals

      Any insights here will be highly appreciated.

      Edited by: 918868 on Mar 5, 2013 7:30 AM
        • 1. Re: Doubt regarding redo log group
          Balazs Papp
          alter system switch logfile;
          alter system checkpoint;

          group is now INACTIVE and you can drop it
          • 2. Re: Doubt regarding redo log group
            Aman....
            918868 wrote:
            I want to drop a particular redo log group , but even after multiple log switches, it's status is either 'Active' or 'Current' , do I have any other better approach to make the status of that particular group 'inactive' rather than continuing the log switching processes in intervals

            Any insights here will be highly appreciated.
            The redo log group would be inactive after the writing of the all the dirty buffers is complete. As mentioned before, issue the command alter system checkpoint and it should make the redo log group inactive more quickly.

            Aman....
            • 3. Re: Doubt regarding redo log group
              sandy121
              Can you kindly explain me why 'checkpoint ' quickens the group to be inactive soon ?
              Can you please kindly share the internals behind these . Thanks in advance.
              • 4. Re: Doubt regarding redo log group
                jgarry
                http://docs.oracle.com/cd/E11882_01/server.112/e25789/startup.htm#CNCPT89043
                • 5. Re: Doubt regarding redo log group
                  sandy121
                  I have that link always handy by bookmarking it, my question is very specific, how does thread checkpoint causd by statement ("alter system checkpoint") make the specific redo log group inactive ?
                  • 6. Re: Doubt regarding redo log group
                    asahide
                    Hi,
                    1.) Thread checkpoints : The database writes to disk all buffers modified by redo in a specific thread before a certain target. The set of thread checkpoints on all instances in a database is a database checkpoint. Thread checkpoints occur in the following situations:
                    <<http://neeraj-dba.blogspot.jp/2011/06/what-is-checkpoint.html>>

                    So, Checkpoint will synchronize the datablocks in the buffer cache with the datafiles on disk, So redo log group become inactive.

                    Regards,
                    • 7. Re: Doubt regarding redo log group
                      Aman....
                      918868 wrote:
                      Can you kindly explain me why 'checkpoint ' quickens the group to be inactive soon ?
                      Can you please kindly share the internals behind these . Thanks in advance.
                      The redo log group would be considered Inactive when all the dirty buffers , whose change vectors are stored in it are written by DBWR to the data file. The command alter system checkpoint forces this write to happen right away. That makes the status change happen in a more quick manner rather than waiting for the DBWR to do it in it's own pace.

                      HTH
                      Aman....
                      • 8. Re: Doubt regarding redo log group
                        ragu.dba.in
                        Hi aman,
                        Your explanations are very simple to understand.I have one doubt.Alter system switch logfile (or) Alter system archive log current (when it is switch from one redo group to another) also issues a checkpoint is't it..? then why a seperate "Alter system checkpoint" command..?

                        Thanks & Regards,
                        ragunath
                        • 9. Re: Doubt regarding redo log group
                          Dude!
                          Alter switch logfile performs a checkpoint in the background. While the switch logfile is instantaneous, the checkpoint may take some time to complete and may not necessarily be successful, for instance, if you run out of disk space or a media error occurs.
                          • 10. Re: Doubt regarding redo log group
                            Aman....
                            ragu.dba.in wrote:
                            Alter system switch logfile (or) Alter system archive log current (when it is switch from one redo group to another) also issues a checkpoint is't it..? then why a seperate "Alter system checkpoint" command..?
                            Both alter system checkpoint and alter system switch logfile come under the thread checkpoint. I am not sure that there is any checkpoint issued with the archive log current command . The reason to have a separate command is just to force the DBWR to do the writing write away rather than letting it happen on it's own pace.

                            Aman....