Re: MUST read Oracle Architecture - Abrief Intro

I think that you will understand it better if you consider 2 scenario's:

1. RMAN backup from time 13:00 is newer then the backup taken at 13:45.
2. You get Enron accounting when the feds discover that invoice number 123 was issued after invoice 124.

There are a lot of things, application and / or system, that can go wrong in this situation.
To be on the safe side shut the database down for 1.25 hours.

Yechiel Adar
Mehish
----- Original Message -----
To: Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com> Sent: Wednesday, July 24, 2002 3:38 PM

> yes , but time based incomplete recovery could create problems if he
doesnt
> take a full
> backup after the os-time-change .
>
> -----Original Message-----
> Sent: Wednesday, July 24, 2002 6:39 PM
> To: Multiple recipients of list ORACLE-L
>
>
> Oracle has no concept wrt. the date & time of Operating System for running
> individually as a product. It just takes the timestamp in certain DML's
> while updating and inserting the rows having DATE as datatype. Nothing
more
> than this.....
>
> Oracle works on the mechanism of SCN ie. System Change Number which gets
> monotonically incremented one by one after every commit takes place. It
has
> nothing to do wrt. the OS time.
>
> When the Oracle engine gets started the control file reads the location of
> datafiles and redo logs and the latest SCN is read and compared with those
> present in datafiles aand redo logs. If the SCN is not matched menas the
> database was abnormally shut down and need thread recovery.
>
> Smon does this task independently and roll forwards the txn's which were
> left in the buffer cache and were not pushed back to d.files during
> checkpoint process. These txn's were committed at the user end.
>
> Now the ones which were not committed would be rolled back internally by
> Oracle b'ground process SMON or Server Process initiated by user process
and
> would rollback the blocks who soever touches them first.
>
> A little bit of ARCHITECTURE OF ORACLE .............. Bye for now.
>
> No problems at the time lagging behind or time forwarding of the OS
>
> -----Original Message-----
> Sent: Wednesday, July 24, 2002 6:00 PM
> To: Multiple recipients of list ORACLE-L
>
>
> Oracle will continue to work fine (as it uses SCN numbers for consistency
> and transaction logging rather than dates). However, if you have any apps
> which use timestamps in the data, then I'd do some more investigation for
> the ramnifications on the application logic side...
>
> -----Original Message-----
> Sent: Wednesday, July 24, 2002 7:13 AM
> To: Multiple recipients of list ORACLE-L
>
>
> If you can take the database down for 1.25 hours.
> I will hesitate to startup the database with time
> less then last closing time.
>
> Yechiel Adar
> Mehish
> ----- Original Message -----
> To: Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com>
> Sent: Monday, July 22, 2002 8:33 PM
>
>
> > Hi Guys,
> >
> > I need to put one hour back for my OS(aix) So How will my database(7.3)
> > handle this?? What steps I have to take?? Any light regarding that??
> >
> > Thanks in advance
> > peter.
> >
> >
> >
> >
> > _________________________________________________________________
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-- 
Please see the official ORACLE-L FAQ: http://www.orafaq.com
-- 
Author: Yechiel Adar
  INET: adar76_at_inter.net.il

Fat City Network Services    -- (858) 538-5051  FAX: (858) 538-5051
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