Re: SCN/ora_rowscn Questions

Right and right, respectively.

On the latter point, please note that the FLASHBACK_SCN value always specifies a SCN value on the source database, whether you're using "impdp" or "expdp". So with "expdp", the use of FLASHBACK_SCN is pretty straightforward, because you're exporting from the source database. But with "impdp" the FLASHBACK_SCN parameter must be used in conjunction with the NETWORK_LINK parameter to copy the data over to the destination database from the remote source database, so the SCN value still pertains only to the source database.

Hope this helps...

Thanks!

-Tim

On 8/12/15 10:30, Woody McKay wrote:
> Thanks Tim. That helps a lot.
>
> Lastly:
>
> On imports, ora_rowscn on table data will get scn's from the DB scn
> and not what was exported? Right?
>
> The only use of the scn in a datapump file would be used for
> flashback_scn? Right?
>
>
> On Wed, Aug 12, 2015 at 12:19 PM, Tim Gorman <tim_at_evdbt.com
> <mailto:tim_at_evdbt.com>> wrote:
>
> Woody,
>
> The Oracle SCN is a six-byte integer implemented in two parts: a
> 4-byte lower-order number and a 2-byte "wrap" counter. As SCN
> value increases, it increments the 4-byte portion, and when that
> hits the 32-bit maximum value, it "wraps" back to zero and the
> 2-byte counter is incremented.
>
> With 48 bits, the maximum SCN value is 281,474,976,710,656 (i.e.
> 281 trillion).
>
> For reference, this allows 16,384 increments per second for about
> 544.7 years.
>
> There is no Y2K issue pending for Oracle anytime soon, but the
> next generation will probably need to deal with it.
>
> Some years ago, there was a bug involving database links which
> caused the SCN to increase very rapidly, bringing the 500 year
> estimate within our lifetime, but that's been resolved, I believe.
>
> Hope this helps...
>
> -Tim
>
>
>
>
> On 8/12/15 9:35, Woody McKay wrote:
>
> Hi all,
>
> I was reading an AskTom article and it talked about the SCN
> wrapping at some point. If this is so, then how large can the
> SCN grow to before it wraps? Where is the wrap count stored?
>
> On imports, ora_rowscn on table data will get scn's from the
> DB scn and not what was exported?
>
> The only use of the scn in a datapump file would be used for
> flashback_scn? Right?
>
>
> Thanks for all answers.
>
> --
> Sincerely,
>
> WoodyMcKay
>
>
> --
> http://www.freelists.org/webpage/oracle-l
>
>
>
>
>
> --
> Sincerely,
>
> WoodyMcKay

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