0 Replies Latest reply: Nov 3, 2011 3:50 AM by 520278 RSS

    Oracle 10g RAC database split mirror replication scenario

    520278
      Hello.

      I am after some advice as to whether:

      a) a particular database replication scenario will work

      b) what could go wrong and how to insure against what could go wrong

      c) what could be done better or easier and

      d) whether there is a better strategy altogether.

      Apologies in advance for the big post !

      I have not done this particular complicated hair-raising procedure before and I am not a DBA (but have used Oracle for many, many years - since version 6 !) so here goes...

      We are in the process of upgrading some RAID 10 SAN hardware.

      We have a large Solaris 10 Sun E25K Oracle 10g ASM RAC database on the current Sun Storage Tek 6140 Brocade 5000 SAN that we want to replicate on the new Brocade AMS 2500 SAN.

      The new database will also have a new server.

      We do not want to bring the database on the current SAN down.

      We are looking at using an RMAN split mirror backup as described at: http://web.njit.edu/info/limpid/DOC/backup.102/b14191/rcmbackp003.htm

      The current database is constantly writing large amounts of data to the current SAN and so it operates in NOARCHIVELOG mode.

      The new database server is connected to both the current and the new SAN.

      So here is the strategy:

      1) Start RMAN on the current database and put the current database into ARCHIVELOG mode

      2) Using RMAN on the current database put the TABLESPACE of the current database into BACKUP mode

      3) Possibly stop the current SAN mirroring (I am not sure yet whether we have to do this or not)

      4) Split the mirror from the current SAN - the mirror has copies of the datafiles of the current database

      5) Unmount the split-off mirror from the current database server and remount it on the new database server

      6) Take the current database out of BACKUP mode and perform recovery on the current database

      7) Put the current database back into NOARCHIVELOG mode

      8) Start RMAN on the new database and perform database recovery on the new database using the copies of the datafiles from the current database on the split-
      off mirror mounted on the new server

      9) Possibly stop the new SAN mirroring

      10) Backup the new database to new datafiles on the new SAN

      11) Set the new database to use the new datafiles on the new SAN

      12) Switch the new SAN mirroring back on

      13) Unmount the split-off mirror from the new database server and remount it back on the current database server

      14) Switch the current SAN mirroring back on

      So will it work ?

      Could it be done better ? Easier ?

      Some questions I have are:

      1) Step 8:

      > Start RMAN on the new database and perform database recovery on the new database using the copies of the datafiles from the current database on the split-
      off mirror mounted on the new server

      To be successful at this will RMAN also need access to the redo logs of the current database ?

      How does that work ? Or does RMAN CATALOG look after all of that ?

      There are warnings in the Oracle documentation about using backed-up redo logs.

      Or is it not a problem as the redo logs come from a different database (the current database) and are being used against the new empty database ?

      Is it necessary to copy and reuse anything else from the current database ?

      I imagine the parameter file and control file of the new database must reflect the future configuration of the new database before RMAN does the data file
      recovery into the new database ? Do we have to create "dummy" datafiles for the new database before RMAN does the recovery ?

      2) Step 10:

      > Backup the new database to new datafiles on the new SAN

      This will take some time ? At least as long, and almost certainly much (?) longer, than an OS copy of the files ?

      Should we instead get the new SAN to mirror the split-off mirror from the current SAN when it is mounted on the new server ?

      That would be faster ? There might be problems are they are two different SAN models.

      3) Does anyone know how good and reliable Brocade and Sun Storage Tek are at splitting and recombining mirrors ?

      4) Can ASM help here ? I know there is ASM mirroring but I think that would take too long if it worked at all ?

      5) Does RAC complicate the situation ?

      Obviously we should have a few trial runs !

      It is a bit like a live organ transplant...

      Thanks for any help and comments.

      It is much appreciated.

      Brett.