3 Replies Latest reply: May 9, 2013 3:03 PM by EdStevens RSS

    Doubt related to incomplete/point in time database recovery using RMAN

    995751
      Hello experts,

      I'm little newbie to RMAN recovery. Please help me in these doubts:

      1. If I have datafiles, archive logs & control files backup, but current online REDO logs are lost, then can I perform incomplete database recovery ?
      2. Till what maximum time/scn can incomplete database recovery be performed ??
      3. What is role of online REDO logs in incomplete database recovery ? Are they required for incomplete recovery ?
        • 1. Re: Doubt related to incomplete/point in time database recovery using RMAN
          EdStevens
          992748 wrote:
          Hello experts,

          I'm little newbie to RMAN recovery. Please help me in these doubts:

          1. If I have datafiles, archive logs & control files backup, but current online REDO logs are lost, then can I perform incomplete database recovery ?
          yes, if you have backups of everything else
          2. Till what maximum time/scn can incomplete database recovery be performed ??
          Assuming the only thing lost is the redo logs, you can recover to the last scn in the last archivelog.
          3. What is role of online REDO logs in incomplete database recovery ?
          They provide the final redo changes - the ones that have not been written to archivelogs
          Are they required for incomplete recovery ?
          It depends on how much incomplete recovery you need to do.

          Think of all of your changes as a constant stream of redo information. As a redolog fills, it is copied to archive, then (eventually) reused. over time, your redo stream is in archivelog_1, continuing into archvivelog_2, then to 3, and eventually, when you get to the last archivelog, into the online redo. A recovery will start with the oldest necessary point in the redo stream and continue forward. Whether or not you need the online redo for a PIT recovery depends on how far forward you need to recover.

          But you should take every precaution to prevent loss of online redo logs .. starting with having multiple members in each redo group ... and keeping those multiple members on physically separate disks.
          • 2. Re: Doubt related to incomplete/point in time database recovery using RMAN
            995751
            Thanks a lot, your answer was indeed helpful.

            Please clear my one more doubt..

            If I recover my DB using command: 'recover database until time'
            How does RMAN come to know the scn from which to start recovery and the stop scn for recovery ?

            Does it only refer control file to get these SCNs or it refers datafile headers for this ?

            Is there any good doc/link to understand this process.. ?
            • 3. Re: Doubt related to incomplete/point in time database recovery using RMAN
              EdStevens
              992748 wrote:
              Thanks a lot, your answer was indeed helpful.

              Please clear my one more doubt..

              If I recover my DB using command: 'recover database until time'
              How does RMAN come to know the scn from which to start recovery and the stop scn for recovery ?

              Does it only refer control file to get these SCNs or it refers datafile headers for this ?

              Is there any good doc/link to understand this process.. ?
              I've never really thought about that question. I'd guess he has to get it from the file headers, and comparing to the control file.