Thanks mark, i really appreciate your response, but i dont think that
delete modfied all the pages, let me put the same question in a
Lets assume that i have a database with 100,000 pages , and 100 pages
has been modifed after full backup.
Whats is really happening when you issue the incremental backup
1. will db2 scan 100,000 pages and see if that page is changed or not
and backup that page if changed , if not just skip that page and
continue to check the rest of pages. If this the case, even if one
page is changed , doest db2 still have to scan 100,000 pages to figure
out which pages were changed? I was under the impression when you turn
on "TRACKMOD" , it will keep track of changes as they occurs and
stored the page information "somewhere" internally and so that db2 can
get the list of pages that were changed by looking at the place where
'TRACKMOD' stores them, I guess this is NOT the way db2 tracks pages
which are changed, right?
When you turn on TRACKMOD, all it does is, just update somewhere in
the page header area that the page is changed, so db2 still have to
scan all the pages to get the list of pages were changed?
I am so confused now, Please explain me how does db2 make a list of
pages were modified to perform the incremental backup?
Many Thanks for your time.
"Mark A" <maswitchboard.net> wrote in message news:<uyXQa.271$1D3.27541news.uswest.net>...> "Siva" <mail2sivaj> wrote in message
> news:8a8e81a1.0307150952.610415b4posting.google.c om...>> > What is real advantage of incremental back up ?
> > I was under the impression, that 'TRACKMOD' will track all the changes
> > made to the database since last full time backup, and it will backup
> > only those pages when do the incremental back up, and i was under the
> > impression when you issue 'incremental backup' db2 can figure pages
> > were changed in no time and backup those changes pretty fast.
> > But in our, we have huge database, we want to implement the
> > incremental testing in our production environement. So we did a test
> > in our test environment, in the test evironment, it would normally
> > takes about one and half hours to complte the full database backup.
> > This is what i did,
> > 1. Turned on 'TRACKMOD'
> > 2. full database backup ( took around 1 and 1/2 hours )
> > 3. deleted around huge amount of data from one table
> > 4. ran a incremental backup command. Guess what? It took me almost the
> > same as full back up ( around 1 hour and 15 mins ), but the size of
> > the backup file is very small comparatively full database backup , but
> > the backup time between full and incremental is almost the same. I was
> > estimated that incremental would be finished within 5 mins.
> > The only advantage i am seeing using incremental back up is, small
> > backup file size.
> > I am guessing that, even though 'TRACKMOD' is on, db2 is checking all
> > the data pages to see if that page is changed or not? Thats why its
> > taking so long as full database backup.
> > Our db2 version 7.3, we are using both DMS and SMS tablespaces.
> > any help will be greatly appreciated. Thanks
> > We have both SMS and DMS tablespaces on the database.
> Are you using version 7.2 with a fixpack level? There is no version 7.3. If
> some rows were deleted from every page when you deleted a "huge amount of
> data from one table," maybe that is why it is taking so long.