6 Replies Latest reply on Jun 29, 2012 11:13 PM by onedbguru

    Continuous Backup

      If I understand it correctly that the RMAN does the continues (24/7) backup of the database files to the FRA at realtime, and once a day (such as 2:00am) offload the data to an external media either tape or disk and/or clouding it via internet.

      If the data files got corrupted, the data stored in the FRA can be used to restore them. Then if the FRA got corrupted, the external backups can be used to recover them. In this case, there will be a gap/lag between the data backed up in the FRA and those on the external media. That means even if system finally gets recovered, some data will still be lost permanently.

      Is it possible for the external backup system to point to the FRA and backup the data on a continuous basis (24/7)? Will this interfere the Oracle's performance?


        • 1. Re: Continuous Backup
          Hello Scott;

          I assume you are talking about Flashback Database.

          Flashback Database uses its own type of log files, called Flashback Database Log Files. So it's not a backup of the database files,
          its a recording images of all changed data blocks in the database.

          Perhaps thinking about the differance bewteen Redo log files and Flashback Log Files will help. Redo log files are used to forward
          changes in case of recovery while flashback log files are used to backward changes in case of flashback operation.

          Is it possible to use an external backup system to backup this up 24/7? Sure you could, but I'm thinking its not the best solution.
          Flashback is a rewind. Its nice to be able to "go back" but since flashback logs reused in a circular manner having extra copies is
          probably just a conflict. Would doing this backup interfere the Oracle's performance? Probably, you are adding I/O you don't need.

          There's a few very good sections on Flashback here :


          If you want zero data loss I'd probably consider Data Guard.

          Best Regards

          • 2. Re: Continuous Backup
            Thanks for the response. By reading the Flashback database, I also learnt some new things along the way.

            At the meantime I would like to apologize not to have presented my question clearly. I actually mean when the Oracle system is running, the live data will be simultaneously backed up to the FRA, (24/7), then at certain time, say 2:00 am in the early morning, the system dump the data to the external backup system (disk, tape, or clouds).

            However, between the live backup to the FRA and lateron copy-over to the external backup system, there is a time lag during which if the FRA gets crashed for some reason, the data in-between will never get recovered, since I can only use the external backup copy to restore the data (which stores the data as latest as 2:00 am in a day).

            So I was asking if there is a way to live-back it up to the fast recovery area and then to the external backup disk/tape/cloud in realtime. So if the FRA gets crashed, I can still use the external copy to restore to the most recent point. But I am not sure if this methodology is feasible?

            • 3. Re: Continuous Backup
              So you really want all the Archive logs so you can recover forward from the last RMAN backup.

              A few ideas

              1. Ship a copy of the archive to an off site server ( might be easier than trying to backup them up continuous )
              2. Set different I/O path locally ( By that say your database is on a SAN, you could add a local drive and have a second DEST_ID for archive )
              3. Data Guard ( OK, I like Data Guard...)

              Does this help?

              There are several High Availability White papers which may also provide solutions :


              Best Regards

              • 4. Re: Continuous Backup
                By the way, does Oracle automatically backup the data files, control files, and redo log files to FRA? If so, is it on a continuous basis (assume the instance runs 24/7)?
                • 5. Re: Continuous Backup
                  No not automatically.

                  Control and redo Can be part of the flashback setup.

                  You can also configure RMAN for Auto control file backup. ( a good idea )

                  Once you have flashback setup RMAN will go there if you take the location out of your RMAN script

                  So if I run something like this :
                  run { allocate channel d1 type disk; 
                  allocate channel d2 type disk;
                  allocate channel d3 type disk;
                  backup full as compressed backupset 
                  database plus archivelog;
                  release channel d1;
                  release channel d2;
                  release channel d3;
                  It will go to FRA if I have it setup.

                  Data files do not go there. The logs hold blocks that have changed for the period you setup. So if you want two days :
                  SQL> alter system set db_flashback_retention_target=2880;
                  I check my flashback area daily and it breaks down like this :
                  Checking free space In Flash Recovery Area
                  FILE_TYPE            PERCENT_SPACE_USED PERCENT_SPACE_RECLAIMABLE NUMBER_OF_FILES                                                   
                  -------------------- ------------------ ------------------------- ---------------                                                   
                  CONTROL FILE                          0                         0               0                                                   
                  REDO LOG                            .39                         0               3                                                   
                  ARCHIVED LOG                       4.47                      4.47              49                                                   
                  BACKUP PIECE                      71.94                     40.65              23                                                   
                  IMAGE COPY                            0                         0               0                                                   
                  FLASHBACK LOG                      2.43                       .02             123                                                   
                  FOREIGN ARCHIVED LOG                  0                         0               0                                                   
                  7 rows selected.
                  I hope this helps. If this is a holiday weekend have a good one.

                  1 person found this helpful
                  • 6. Re: Continuous Backup
                    scottjhn wrote:
                    By the way, does Oracle automatically backup the data files, control files, and redo log files to FRA? If so, is it on a continuous basis (assume the instance runs 24/7)?
                    To FRA, yes, but not continuously. That is an interesting [false] concept of RMAN. You can configure a job that executes at a given time as your backup window allows. Like databases that can take > 24hrs to do a consistent backup.
                    1 person found this helpful