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Archive for May, 2011

Protecting Archive Logs in the Event of a Disaster

Posted by sdefilip on May 6, 2011

 Summary of Methods to Protect Archive Log Tapes

 I have a client who is concerned about losing archive logs and being able to recover their database in the event of a disaster.  We take full RMAN backups, including archive logs and control files every night, but the concern is what would happen if their server is destroyed in between these backups. With the knowledge that a full Disaster Recovery Plan is not a simple undertaking and that they would need more than archive logs to recover their database in case of the destruction of their server, they asked me to provide options which I am sharing on this blog.  I am sharing the results of this undertaking. The environment is AIX 6.5 and Oracle 11.2 Standard Edition.  Please feel free to comment and share your suggestions.

 Options to protect archive log tapes (and the full database) are:

 I.  Have RMAN take more frequent backups, including archive logs.

II. Oracle allows specification of an alternate destination for archive logging that is 

     additional to the primary destination. 

      NFS mount a directory on a remote server. Use an alternate “archive_log_dest”    parameter to specify the NFS mounted remote directory as the alternate log destination.

III.  SFTP or rsynch a copy of the archive logs to a remote server through a shell script. The shell script would have to:

  1. check the V$ARCHIVED_LOG view to determine if each archive log file in the archive log directory has completed its archiving process.
  2. use the AIX rsynch command (or SFTP) to synchronize the remote archive log destination with the primary server archive log destination
  3. run this script every nn time intervals, leaving a window for the RMAN backups

IV. Use the pre-RMAN method of database backup. Copy the database user datafiles, control files, archive logs and parameter file to a directory on an NFS mounted remote server directory. This requires that an Oracle instance is installed on the remote server to recover the database from these files. This method has it’s weaknesses and so RMAN was created and offered as an alternative.

V.  Use RMAN to rig a standby database without DataGuard or GoldenGate;

      this involves another Oracle instance running on the remote server, use of 

    RMAN to clone the primary database, shipping primary database RMAN backup

    files to remote server and, finally, running an RMAN recovery of the database on

   the remote server.

VI.  Create an Oracle RAC 2-node cluster with one cluster being on a remote server.

       I believe that this is possible with 11.2 tandard Edition, possibly with a small

       charge per node.

 I recommend option “III” because it does not require another instance of Oracle on the remote server, it will not slow down the log writer Oracle process (LGWR) which would most likely result in a general database slowdown. In addition, the AIX/network resources used, if the script is not run very excessively, should not be sufficient to slowdown the Oracle database or the application.  My suggestion is to determine the average amount of time that the database takes to fully archive a log, decide how many logs you would like copied at the same time and use that average as a guideline to determine how frequently to schedule the script.

 
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