RE: ** fall back backups

Having nothing at all to do with Oracle databases per se, I have long
advocated a total system outage in excess of one hour for "fall back." IF
(note the "if") this does not cause a material inconvenience to your
business once a year between 1 AM and 3 AM Sunday morning, then it is an
opportunity to completely eliminate time warp file stamps and events in your
entire system. Notice that this in not needed at all for "spring ahead", or
ever if you run your system on constant timeframes (like GMT worldwide).

This has nothing whatever to do with any particular known problem and
everything to do with the improvement in certainty about what happenned when
and establishing a sequence of events. If the value of easily establishing
an order of events is less than the cost of shutting down for a small window
once a year, then don't do it.

Handling "fall back" has in fact escaped the imagination of many overall
applications systems designers over the years. Unless shutting down is
really pretty inconvenient, I prefer to skip the test.

I can't remember if anyone has actually implemented a "run slow" timer to
nearly completely eliminate all problems by running the wall clock at half
speed for two hours beginning at 1 AM. I do remember discussing that with
vendors in the early to mid 1990's in conjunction with MOSES.

Regards,

mwf
  -----Original Message-----
  From: oracle-l-bounce@xxxxxxxxxxxxx
[mailto:oracle-l-bounce@xxxxxxxxxxxxx]On Behalf Of Mercadante, Thomas F
(LABOR)
  Sent: Monday, October 31, 2005 7:40 AM
  To: jcave@xxxxxxxxxxx; ajoshi977@xxxxxxxxx; oracle-l@xxxxxxxxxxxxx
  Subject: RE: ** fall back backups


  Justin,



  I agree.  I have never bounced the database because of clocks changing.
All should be aware of when the sysadmins changed the clocks on the database
server though.  Especially if you are in a recovery situation!



  Tom




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  From: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx]
On Behalf Of Justin Cave (DDBC)
  Sent: Sunday, October 30, 2005 9:27 PM
  To: ajoshi977@xxxxxxxxx; oracle-l@xxxxxxxxxxxxx
  Subject: RE: ** fall back backups



  Did the analyst in the TAR say why he was recommending rebooting the
database?  I've never rebooted a database just because the clock changed and
I can't see why it would make a difference.  Doing a point-in-time recovery
to a time between 1 and 2 AM (clocks went back an hour at 2 AM) will be
problematic regardless of whether or not you reboot, but SCN based recover
won't have a problem.



  There may be applications out there that do not handle daylight savings
well (i.e. a DATE column as a primary key that gets duplicates), in which
case you may do something like take the server offline for an hour while the
clock changes.  As a general rule, though, there is no need to bounce a
database just because you changed the operating system's clock.



  Justin Cave  <jcave@xxxxxxxxxxx>

  Distributed Database Consulting, Inc.

  http://www.ddbcinc.com




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  From: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx]
On Behalf Of A Joshi
  Sent: Sunday, October 30, 2005 8:43 PM
  To: oracle-l@xxxxxxxxxxxxx
  Subject: ** fall back backups



  Hi,

    Now that clocks have been set back one hour (in us of a etc), it is time
to bounce the databases. Since Oracle says it needs to be done (read some
analyst in a TAR said it).

  Is it for backups? I agree time based recovery to a point in time could
lead to issues. However, will it affect the regular recovery until cancel
which I think goes by SCN/log #. Please correct me if I am wrong.

  Also once you have a couple of backups after the fall back resetting of
clock is it still necessary to bounce databases and immediately take 2
backups?

    Apart from backups does setting the clock back affect anything else on
the database? Thanks


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