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RE: Responses : About Older Backups -- was Re : RMAN-NetBackup w ithout an RMAN Catalog

Date: Sat, 16 Oct 2004 19:11:33 -0500
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   I think you have raised some important issues here. Your requirements are not unreasonable. Today I don't believe the computer industry is much concerned about long-term retrieval of data. Vendors stay in business by responding to customer demand and today customers are not demanding long-term data retrieval. As computers become more important to our society, this issue will soon be treated more importantly. In my reading of this topic, here are some ideas I have heard:

  1. Keep the data on-line. Our ERP system has every record since it was started 7 years ago, which ensures all that data is accessible.
  2. Move the data into a data warehouse. This is exactly what a DW is designed to do. Capture data with the proper context.
  3. Store the data in a format and medium that is most resistant to obsolescence. Oracle has kept the export format compatible over many major version releases. I haven't seen any commitment with respect to RMAN formats. Therefore export would be favored over RMAN. As someone pointed out, ASCII flat files are even more resistant to obsolescence.
  4. Periodically test the recoverability of old data. For example, reload all backups annually. If a problem is found, you are more likely to successfully resolve a problem that has occurred in the last year than if you allow a decade to elapse.
  5. Carefully determine the specific purposes for maintaining access to old data and develop tests to ensure that access is still maintained.
  6. Upgrade old data sets. For example, if you upgrade your Oracle version, restore all archived data sets and convert them to the newer Oracle version. Same with a new hardware platform or O.S. upgrade. Then re-save them on fresh media. Expensive, but effective.
  7. Consider purchase of a product specifically designed for data archiving.
  8. The computer industry is volatile. Do not assume that any vendor will be in business 5 years from now or that they are still producing products compatible with those you use today.

As to RMAN itself, I regularly conduct disaster recovery tests. You can recover RMAN backup sets written to tape if you have a copy of the controlfile taken immediately after the backup. My practice is to separately copy the controlfile to tape to ensure its availability. You can also extract the controlfile from the RMAN backup itself, but since I haven't tested this I don't rely on it. All that is required is that you have the same Oracle version that you used to create the backup. Nothing in this method depends on time except the availability of that same Oracle version.

Dennis Williams
Lifetouch, Inc

Received on Sat Oct 16 2004 - 19:08:18 CDT

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