Re: NTP on linux box was ahead of 5 hrs

A recovery should use SCN and not the date/time stamp of the change.  I have had no issues restoring databases backed up prior to a time change (daylight savings to standard, where an hour is repeated) as Oracle recovered via the SCN recorded in the controlfile.  I do agree that key values,if based on SYSDATE, will be off considerably because of the 5 hour shift but that shouldn't affect SCN generation.
 
It has been a while since I had to restore from a backup taken when both DST and standard time were applied to inserts and updates (as on the DST to Standard time change weekend with a 24/7 application) but I don't recall any issues from the recovery.

David Fitzjarrell




On Monday, November 18, 2013 9:10 AM, nilesh kumar <nileshkum_at_gmail.com> wrote:
  
Thanks Martijn, 

Suppose this database belongs to a Banking sector, and few users perform the transaction when NTP was 5 hrs ahead. And Suppose if user asks the details of their transaction in that case we are in bit confusion state right.  

In general I was checking with everyone, if someone has faced this kind of issue and the work around they did to fix this one. 

Thanks for replying Martijn 

Thanks 
Nilesh

 
On Mon, Nov 18, 2013 at 8:10 PM, Martijn Bos <maboc_at_maboc.nl> wrote:

Hi,
>
>See my ideas inline.
>
>Best Regards,
>Martijn
>
>
>Best Regards,
>Martijn
>
>
>
>On Mon, Nov 18, 2013 at 07:03:32PM +0530, nilesh kumar wrote:
>> Hello All,
>>
>> NTP was running ahead of 5 hrs of normal time on Linux box.
>>
>> We have oracle database running on that server version 10g.
>>
>> Network team tried to synchronize the NTP and they synchronized the NTP on
>> the server.
>>
>> >From oracle database endi have few questions.
>>
>> I took a levelzero backup and all archive log backup immediately and asked
>> the application team to release all the conections to the database and
>> connection refresh so that none of the users are connected to the
>> database, and then bounced the db and again took a level zero backup.
>>
>> Am i missing any thing in this case that need to be taken care.
>>
>> few more question in mind:-
>> ----------------------------------------
>>
>> Database was running and users were connected to the database during this
>> issue occured, if some users committed the transactions and when NTP was 5
>> hrs ahead and does any inconsistency occur after the NTP was synchronized.
>
>The database ticks around scn's so, on a 'physical' level I do not expect inconsistencys.
>On a logical level (data-model), you may expect inconsistencys when 'sysdate' has been used to fill some rows.
>(Also think of RI where sysdate is used in a column)
>
>
>>
>> ----------------------------------------
>> This has not occured but have a question for the below conditon.
>> If suppose the DB would have crashed after the NTP synchronization and
>> backup taken last sunday level zero, till what time would we able to
>> recover the DB, as few archives have generated after when the NTP was 5 hrs
>> ahead in time.
>>
>
>I think that a Point In Time recovery will be a little hazardous.
>In this case I would try to restore to a sequence number or even a scn.
>
>I _think_ that a restore would restore to the time before the re-syncronaziation (the first time that time x appeared).
>
>
>> Please advise
>>
>> Thanks
>> Nilesh
>>
>>
>>
>> --
>> Thanks & Regards
>> Nilesh
>> Oracle DBA (sqlplus "/as sysdba" is my world)
>>
>> "As our circle of knowledge expands, so does the circumference of darkness
>> surrounding it."--Einstein
>> "All men die, few men ever truly live" -- Braveheart
>> "You can get help from teachers, but you are going to have to learn a lot
>> by yourself, sitting alone in a room." --Dr. Seuss
>> "Know me for what I do and for not what I am. Judge me for what I can do
>> and not for what I have done."-Unknown
>> "Don't walk in front of me, I may not follow. Don't walk behind me, I may
>> not lead. Just walk beside me and be my friend."- Albert Camus
>> "Never argue with an idiot. They drag you down to their level and then beat
>> you with experience." - Unknown
>>
>>
>


-- 
Thanks & Regards
Nilesh
Oracle DBA (sqlplus "/as sysdba" is my world)

"As our circle of knowledge expands, so does the circumference of darkness surrounding it."--Einstein
"All men die, few men ever truly live" -- Braveheart
"You can get help from teachers, but you are going to have to learn a lot by yourself, sitting alone in a room." --Dr. Seuss
"Know me for what I do and for not what I am. Judge me for what I can do and not for what I have done."-Unknown
"Don't walk in front of me, I may not follow. Don't walk behind me, I may not lead. Just walk beside me and be my friend."- Albert Camus
"Never argue with an idiot. They drag you down to their level and then beat you with experience." - Unknown 

--
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