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Re: Backup trends (2): HOT or COLD

From: JEDIDIAH <jedi_at_nomad.mishnet>
Date: 14 Apr 2004 16:24:23 -0400
Message-ID: <slrnc7r7cl.43n.jedi@nomad.mishnet>

On 2004-04-09, Howard J. Rogers <> wrote:
> On 9 Apr 2004 14:29:28 -0400, JEDIDIAH <jedi_at_nomad.mishnet> wrote:
>> On 2004-04-03, Howard J. Rogers <> wrote:
> [snip]
>>> So yes, it has lots of nice features. But those are merely incidental
>>> to the
>>> real reason why you should use RMAN in preference to O/S scripts:
>>> performance. RMAN doesn't cause the database to generate 20 or 30 times
>>> the
>>> amount of redo per transaction that O/S hot backups do. RMAN doesn't
>>> hammer
>> Certainly a valid point.
>>> one data file to death before moving on to another, but instead
>>> multiplexes
>>> across many datafiles, little bits being taken from each one in turn.
>>> RMAN
>> This is a just a simple coding and configuration issue.
> The "cp" command takes an argument that specifies 'the first X bytes of a
> file', does it? Or 'the next Y bytes after that'?

This sort of functionality isn't required for the features specified. The equivalent of an interleaved tarball isn't necessary to achieve parallelism.

> Didn't think so.
> In which case, no "simple coding" on your part is going to resolve the
> issue.
> RMAN is NOT doing a cp. That's the point.

Yes. It makes the resulting product remarkably more complicated to deal with pretty much requiring that RMAN be used to pull it apart again.

>> If you take our
>> korn coding as seriously as the rest of your DBA duties, this should
>> never be a problem.
>>> parallelises in a way no O/S script never could. And you can throttle
>>> the
>>> I/O rate up or down for RMAN to minimise the impact on the production
>>> database or to maximise the speed at which the backup is done.
>> Any of this can be crudely estimated using less complicated tools.
> I'm not talking about estimating I/O rates. I'm talking about *setting* an
> I/O rate so that the backup operation does not hog hard disk resources to
> the exclusion of performance by ongoing regular users. Does the "cp"
> command take an I/O rate argument?

It doesn't need to. This is Unix. You can use the other n-thousand utilties on the system to determine the impact of your cp's and act accordingly.

> It's pretty sad if you think RMAN in 9i is "complicated".
> How complicated is "backup database;"??

It's quite complicated should you ever desire to pull apart the end result with a hex editor. I don't view Oracle as the whole world. It's simply not prudent.

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Received on Wed Apr 14 2004 - 15:24:23 CDT

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