RE: reset the SCN for the database

From: Goulet, Richard <Richard.Goulet_at_parexel.com>
Date: Wed, 15 Jul 2009 14:32:47 -0400
Message-ID: <23C4836D8E9C5F4280A66C0C247BC16F2B106DD9_at_US-BOS-MX011.na.pxl.int>

Humm, there is 60 seconds in a minute, 3600 in an hour, 86400 in a day, 31,536,000 in a year and 15,768,000,000 in 500 years. So at 16K commits per second that makes the largest SCN = 252,288,000,000,000 which is one heck of a lot of transactions.  

Dick Goulet
Senior Oracle DBA
PAREXEL International  

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From: oracle-l-bounce_at_freelists.org
[mailto:oracle-l-bounce_at_freelists.org] On Behalf Of K Gopalakrishnan Sent: Wednesday, July 15, 2009 2:22 PM
To: TESTAJ3_at_nationwide.com
Cc: hrishys_at_yahoo.co.uk; oracle-l_at_freelists.org; oracle-l-bounce_at_freelists.org
Subject: Re: reset the SCN for the database

Joe,  

Going by the standard answer, it will take around 500 yeras for you to run out of SCN with 16K commits/sec. So there is no way you will run of SCNs in (y)our life. Also the SCN structure has an internal limitation of increment values. It can not be incremented to arbirarily high values. So you can not use the ADJUST_SCN or _minimum_giga_scn to reach the limit :)  

So technically speaking the first error you may get with currnet versions of will be ORA-1513, but you will get umpteenl ORA-1558s as all the rollback segments would have dead by that time.

Best Regards,
K Gopalakrishnan

Oracle Database 10g Real Application Clusters Handbook http://www.amazon.com/gp/product/007146509X/

Oracle Wait Interface: A Practical Guide to Performance Diagnostics & Tuning
http://www.amazon.com/exec/obidos/tg/detail/-/007222729X/

On Wed, Jul 15, 2009 at 12:13 PM, <TESTAJ3_at_nationwide.com> wrote:

        A discussion many years ago asked "what happens if you run out of SCNs?" Curious minds still want to know or has this already been answered.         

        joe         

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	Joe Testa, Oracle Certified Professional 


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From: 	K Gopalakrishnan <kaygopal_at_gmail.com> 
To: 	hrishys_at_yahoo.co.uk 
Cc: 	oracle-l_at_freelists.org 
Date: 	07/15/2009 01:08 PM 
Subject: 	Re: reset the SCN for the database 
Sent by: 	oracle-l-bounce_at_freelists.org	

________________________________




	Hrishy, 
	  
	Resetlogs does not reset the SCN. It just resets the LSN (Log

Sequence Number), thats why it is RESET-LOGS. You can advance SCN by ADJUST_SCN event (which goes only forward btw). You may consider FLASHBACKS to go back to the past.           

        -Gopal         

        On Wed, Jul 15, 2009 at 4:44 AM, hrishy <hrishys_at_yahoo.co.uk <mailto:hrishys_at_yahoo.co.uk> > wrote: Hi   

One of my environment makes use of streams and if i do a incomplete recovery using resetlogs the SCN would be reset.How do change the SCN to make it go back to what it was earlier.      

regards
Hrishy                   

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Received on Wed Jul 15 2009 - 13:32:47 CDT