RE: What happens during open resetlogs?

That's normal, SCN for a database is ever-increasing, you can not roll it back even with RESETLOGS open. The RESETLOGS_CHANGE# will be set to current SCN during a RESETLOGS operation.  

Only the log sequence numbers are reset to zero due RESETLOGS, not SCN. And the log sequence number is something which resides in controlfile, not datafile headers. Internally only the SCN's matter for deciding whether a log is needed for recovery or not, log sequence numbers are here just for our convenience again.  

If Oracle did reset the database SCN back to zero during RESETLOGS then we would have to go through every block in datafiles and reset the last update SCN in their headers back to zero as well, lot's of functionality is dependent on that info. Also, all undo segments would need to be reset, etc. Even when you plug a transportable tablespace with much higher SCNs in to your database, then Oracle has to bump up SCN to match the highest SCN in the datafile headers.  

Oracle doesn't ever reset SCN back for a database, it's only the changed RESETLOGS_CHANGE# which determines a new incarnation of the database, all other things going on are done just for our convenience...  

Tanel.  

From: oracle-l-bounce_at_freelists.org [mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Ram Raman
Sent: Thursday, August 24, 2006 04:37
To: tanel.poder.003_at_mail.ee
Cc: alever_at_libero.it; oracle; oracle-l
Subject: Re: What happens during open resetlogs?

I recently cloned and opened a database with resetlogs option. I thought I would find the RESETLOGS_CHANGE# to be something like 1 or 10, instead I found it to be some 17 digit number carried over from production. Any thoughts on that.  

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