1 2 3 Previous Next 40 Replies Latest reply: Feb 18, 2013 8:32 PM by yxes2013 Go to original post RSS
      • 31. Re: Can archivelog history in the v$table be full?
        EdStevens
        yxes2013 wrote:
        Thanks Hem,

        Hmmm I am confused....So if my database crashed for the day and I have a backup last night, + plus I have redos intact I do not have to worry lost transactions? even if I do not have archived logs?

        The scenario is like this:
        Archiving turned off.
        The system.dbf got removed accidentally or got corrupted.
        I need to restore from backups last night and recover the transactions for the day stored in the redos. Is it possible?
        I am thinking that all the online redo logs still holds all the transaction for the day.
        Scenario is like THIS:

        07:00) Database starts up for the day. All you have is the cold backup taken prior to startup, and you stated you do not want to take archivelogs.
        07:30) Database activity fills redo-1, switch to redo-2
        08:00) Database activity fills redo-2, switch to redo-3
        08:30) Database activity fills redo-3, switch to redo-1
        09:00) Database activity fills redo-1, overwriting activity from 7:30 to 8:00, switch to redo-2
        09:30) Database activity fills redo-2, overwriting activity from 8:00 to 8:30, switch to redo-3
        10:00) Database activity fills redo-3, overwriting activity from 8:30 to 9:00, switch to redo-1
        10:30) Database activity fills redo-1, overwriting activity from 9:00 to 9:30, switch to redo-2
        11:00) Database activity fills redo-2, overwriting activity from 9:30 to 10:00, switch to redo-3
        11:30) Database activity fills redo-3, overwriting activity from 10:00 to 10:30, switch to redo-1
        12:00) something bad happens to a data file.

        Now, how are you going to recover those transactions from 7:00 to 10:30 ????

        Please explain to your company's management that you lost 3 1/2 hours worth of transactions because you didn't want to learn how to use the fundamental backup and recovery tool provided with the database.

        Edited by: EdStevens on Feb 15, 2013 6:58 AM
        • 32. Re: Can archivelog history in the v$table be full?
          Hemant K Chitale
          The OP is talking of 10 Redo Log Groups of a large size -- e.g. 1GB.
          Assuming that the total redo generation between two cold backups does not exceed 10GB, he should be able to restore and recovery from last night's backup using the online redo logs (without any archives). That also assumes that only datafiles are lost (corrupt) and not online redo logs !


          Hemant K Chitale
          • 33. Re: Can archivelog history in the v$table be full?
            yxes2013
            So are you convinced ed? ;)
            • 34. Re: Can archivelog history in the v$table be full?
              Hemant K Chitale
              I know that it is possible. But you must build a test case and prove it to your managers.

              You do know that you run a risk of an online redo log file being corrupted.
              (With ARCHIVELOG implementation, most sites would backup the archivelogs to tape frequently).


              Hemant K Chitale
              • 35. Re: Can archivelog history in the v$table be full?
                yxes2013
                Thanks dear :),

                I have two redo groups, one on raid and one on local disk /root/redo ;)
                • 36. Re: Can archivelog history in the v$table be full?
                  EdStevens
                  yxes2013 wrote:
                  So are you convinced ed? ;)
                  No.

                  I fully understand Hemant's point.

                  My question to you is, are you willing to bet your company's data on the idea that you will never, ever completely fill all of your redolog groups between backups AND will never, ever lose a complete redo log group? ON that second point, aside from any mis-guided faith you place in your hardware, let me ask two more questions. First, what is the name of your redolog files? Second, what is your SA going to do when he thinks he's running out of disk space, and in looking for candidate files to delete, sees a bunch of files named something.*log*?
                  • 37. Re: Can archivelog history in the v$table be full?
                    Hemant K Chitale
                    I have two redo groups, one on raid and one on local disk /root/redo
                    I hope that you mean that you have two members in each group (and, say, 10 groups of 1GB each).

                    Hemant K Chitale
                    • 38. Re: Can archivelog history in the v$table be full?
                      yxes2013
                      Yeah, thats what I meant :)

                      But I also understand Ed's point and I know he is right ;)
                      I am just making a scenario where it can be possible to happen for the sake of argument discussions, and not really to recommend it.

                      Edited by: yxes2013 on 18.2.2013 17:59
                      • 39. Re: Can archivelog history in the v$table be full?
                        yxes2013
                        By the way for the sake of discussion, How do I check if may data which was first entered/updated in the morning, Is still found in my 10 online redo logs ? Is it thru data mining?
                        • 40. Re: Can archivelog history in the v$table be full?
                          EdStevens
                          yxes2013 wrote:
                          Yeah, thats what I meant :)

                          But I also understand Ed's point and I know he is right ;)
                          And so is Hemant. He and I are in agreement. We are just pointing different aspects and considerations of the same principle.

                          I am just making a scenario where it can be possible to happen for the sake of argument discussions, and not really to recommend it.

                          Edited by: yxes2013 on 18.2.2013 17:59
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