Re: Control file recovery

On 5 Sep 2005 06:54:44 -0700, "Pradeep" <agarwalp_at_eeism.com> wrote:

>Thanks a lot Sybrand,
>
>One thing i am not able to understand, If we specify the correct online
>log file, then why do we have to specify Resetlogs. Is it that, the
>current log sequence number cannot be updated in the restored Control
>file and RESETLOG is the only way to update the control with a Sequence
>number (which is 1)?
>
>Thanks a ton

The controlfile is from a backup. Your scenario is relatively simple. There might be datafiles coming from backups, there might be datafiles current.
How is Oracle to decide which SCN and logsequence is correct? This is *always* derived from the controlfile, but the controlfile is from a backup. So who can tell? Should Oracle assume it is always the highest SCN and logsequence? One might end-up in recovery after recovery, because if there are different SCNs and LOGSEQUENCES in various files, choosing ONE of them, would force Oracle to perform further recovery. So, yes, the number could be updated, but we can't *trust the number to be correct*, and Oracle won't allow datafiles etc in different stages, because for Oracle a database is an unity.

--
Sybrand Bakker, Senior Oracle DBA