Re: Silly question about backups of live systems...
Not entirely true.
To answer the first question " I start the back up at Midnight, and at
12:01, someone inserts a record." the answer is IT DEPENDS.
It depends on what you consider the archive starting point. The archive
starts not when you submit the archive command (ontape -s or onbar -b )
but when the archive checkpoint has completed.
All changes after the archive checkpoint (insert, updates, deletes) will
not be in the archive.
Also Logical log pages are necesary at the end of the archive always
(Though we do not need to make a special log backup if a whole system
archive is restored as the pages in the logical logs wuld be enough) ,
even if it is a whole system archive (ontape -s or onbar -b -w) because
we need to rollback the transactions that were open at the moment of the
archive checkpoint.
On Top of this we can have parallel dbspace archives. If you restore the
instance from a dbspace parallel archive ( A must if you wanted parallel
archives before 11.10) then you will have a set of dbspaces backed up at
different points in time (Each dbspace using a different archive
checkpoint) and logical logs ARE needed. IN this case is more difficult
to answer the 12:01 question , as we would need to know at what point
the last archive checkpoint occured as that would be the lowest point at
which the instance can be recovered
Art Kagel wrote:
> Whan it finishes copying the contents of each dbspace the archive
> process will append all of the physical log pages that were created
> during the archive up until that point for the dbspace that just
> completed. The physical log pages written during an archive are
> copied from the physical log to a set of temp tables, one per
> dbspace. Once the dbspace is completed and its pre-images have been
> dumped to the archive, that temp table is dropped and log pages for
> that dbspace are no longer copied.
>
>
> \\So during the restore, initially the copy on disk is inconsistent as
> it contains pages that were flushed to disk after the archive
> started. However, those physical log pages are then also written to
> disk overwriting the changes since the archive started with the page
> images that existed at the time of the start of the archive. Poof,
> consistency. That is the innovation that created the first Informix
> OnLine server which was the first server that could take a consistent
> archive while the server was being actively updated.
>
> Art
>
> Art S. Kagel
> Advanced DataTools (www.advancedatatools.com
> <http://www.advancedatatools.com>)
> IIUG Board of Directors (art@iiug.org <mailto:art@iiug.org>)
>
> Disclaimer: Please keep in mind that my own opinions are my own
> opinions and do not reflect on my employer, Advanced DataTools, the
> IIUG, nor any other organization with which I am associated either
> explicitly, implicitly, or by inference. Neither do those opinions
> reflect those of other individuals affiliated with any entity with
> which I am affiliated nor those of the entities themselves.
>
>
>
> On Mon, Jun 21, 2010 at 6:19 PM, Ian Michael Gumby
> <im_gumby@hotmail.com <mailto:im_gumby@hotmail.com>> wrote:
>
> Silly question.
>
> Suppose I have a large table and I'm backing it up for a point in
> time archive.
>
> The back up is done on a live system, so you have people inserting
> rows while the backup is running.
>
> Will those rows become part of the back up?
>
> An example... I start the back up at Midnight, and at 12:01,
> someone inserts a record.
> What happens?
>
> Thx
>
> -G
>
>
> ------------------------------------------------------------------------
> The New Busy think 9 to 5 is a cute idea. Combine multiple
> calendars with Hotmail. Get busy.
> <http://www.windowslive.com/campaign/thenewbusy?tile=multicalendar&ocid=PID28326::T:WLMTAGL:ON:WL:en-US:WM_HMP:042010_5>;
>
> _______________________________________________
> Informix-list mailing list
> Informix-list@iiug.org <mailto:Informix-list@iiug.org>
> http://www.iiug.org/mailman/listinfo/informix-list
>
>
> ------------------------------------------------------------------------
>
> _______________________________________________
> Informix-list mailing list
> Informix-list@iiug.org
> http://www.iiug.org/mailman/listinfo/informix-list
>