Re: SCN Jumping issue

From: Riyaj Shamsudeen <riyaj.shamsudeen_at_gmail.com>
Date: Thu, 26 May 2016 08:50:56 -0700
Message-ID: <CAA2DszxhisdDENOw_zEX9+m=Ete78GDpjERuDL0vMRDLWJUJxw_at_mail.gmail.com>

Hello Deepak,
  Your assertion is correct, database link sessions will synchronize the SCN between the databases, thereby, increasing the SCN of one or more databases sharply.

  So, if any one of your database is encountering from the bug, then, all databases interconnected through database links can suffer the consequences. You may be using RMAN backup, however, some database connecting to your database over database link(s) might be using database level 'begin backup' command, infecting your database SCN value too.

  This will be an hard issue to debug: You need to identify if any of the database connecting to your database, directly or indirectly, is using 'alter database begin backup' command and if so, does that database have the bug fix for the issue ?

  Yeah, 55 days seems serious, if the database is affected by the bug, you can consume 55 days in a matter of days (if not hours).

Cheers

Riyaj Shamsudeen
Principal DBA,
Ora!nternals - http://www.orainternals.com - Specialists in Performance, RAC and EBS
Blog: http://orainternals.wordpress.com/ Oracle ACE Director and OakTable member <http://www.oaktable.com/>

Co-author of the books: Expert Oracle Practices <http://tinyurl.com/book-expert-oracle-practices/>, Pro Oracle SQL, <http://tinyurl.com/ahpvms8> <http://tinyurl.com/ahpvms8>Expert RAC Practices 12c. <http://tinyurl.com/expert-rac-12c> Expert PL/SQL practices <http://tinyurl.com/book-expert-plsql-practices>

<http://tinyurl.com/book-expert-plsql-practices>

On Wed, May 25, 2016 at 9:15 PM, Deepak Sharma <dmarc-noreply_at_freelists.org> wrote:

> Just recently (last week) we came across an alert from OEM for one of our
> primary databases, related to SCN Jumping or increasing very rapidly.
>
> We already have an Oracle SR in place, but wanted to check with the
> community about their thoughts in case someone has had similar experience
> in the past (and any solution).
>
> This is an Oracle 11.2.0.4 database (1) using RMAN backup, and (2) has
> several connections coming over using database links to it (research shows
> the issue could be db link related).
>
> Some of the other DBs that have DB Links to ours, see messages related to
> sudden increase of SCNs for their own DBs, in alertlog (fyi).
>
> The OEM alert seem pretty serious, and says we have about 55 days before
> the DB would freeze temporarily or throw ORA-600 errors.
>
> Could be related to this :
>
> https://community.oracle.com/thread/2336601?tstart=0
>
>
>
>

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Received on Thu May 26 2016 - 17:50:56 CEST