Re: backup and recovery question

A copy of this was sent to Tansel Ozkan <tansel_at_openix.com> (if that email address didn't require changing) On Wed, 14 Oct 1998 15:08:25 -0400, you wrote:

>Our system administrator brought up an interesting point:
>
>I know that a backup of Oracle files for a open database
>in NOARCHIVELOG mode will not startup the database. However,
>I was not able to give a good explanation for the following
>question:
>
>What is the difference between a
>database started after a machine crash due to a power loss
>and a database started with all Oracle files copied at exactly
>same point in time for a database running in NOARCHIVELOG mode
>and when the database is open.

one of the differences is that you cannot INSTANTANEOUSLY copy all files at exactly one single point in time when the database is open.

A crash happens instantly. A copy is measured in somewhat longer timeframes. During the copy the files are getting horribly inconsistent with each other. Also, during this period of time, redo is being generated perhaps and if it wraps, we will reuse a redo file that perhaps one of the datafiles will need upon recovery (but we won't have it).

So, if you could copy files as fast as a system could crash (zero amount of time) we wouldn't even be having this discussion since backing up an infinitely large database would take 0 seconds -- so shutting it down properly to backup and restart would take seconds or minutes -- backing up would be great....

>
>Would an Oracle instance recovered using these set of files
>perform an instance recovery at startup?
>
>Thanks..
>
>Tansel
 

Thomas Kyte
tkyte_at_us.oracle.com
Oracle Government
Herndon VA

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