Re: DIFFFULL Backups with TSM for SQL

Jeff,

This is probably a good question to post the
the Microsoft SQL Server forums.

TDP for SQL simply takes a "blob" of data
that the SQL Server hands it and stores it
on the TSM Server. TDP for SQL does not
make the determination of what data should be
backed up and what shouldn't. SQL Server
decides all of this.

TDP for SQL tells SQL Server that it wants to
perform a "differential" backup, then waits
for the SQL Server to hand the data back.

The DIFFESTIMATE option allows you to estimate
this since SQL does not give you a way to
determine this without actually scanning
all database pages.  That estimate is only
used to initially reserve space on the
TSM Server... it is not used as the
actual amount of data to be backed up.

Thanks,

Del

----------------------------------------------------

Del Hoobler
IBM Corporation
hoobler AT us.ibm DOT com

- Never cut what can be untied.
- Commit yourself to constant improvement.

=========================================================

> Have installed TSM for MS SQL (vand i am now testing backup/recovery. I
> have a test SQL server i can play with and this has 10 databases, i
exclude
> 9 and only backup 1 at the moment, for testing.
> In the DSM.OPT, i have
> INCLUDE \...\database-name\...\*      to backup just one of the ten
> databases
> EXCLUDE \...\*                                           so that i can
> exclude the other nine databases
>
> I understood from the docs that if I backup a SQL database using FULL,
then
> a DIFFFULL backup (which i ran 5 minutes later) would only backup changes
> since the last full backup.
>
> Having ran a FULL backup, it dumped approx. 270mb of data from a single
> database. When i ran the DIFFFULL backup, it dumped 57mb. The problem
here
> is that this is a test NT server, and no-one is accessing (therefore
> updating) data, so why did the DIFFFULL dump 57mb when nothing has
changed?
> I read about a DIFFFULL % in the .cfg file, and that it defaulted to 20%.
I
> changed this to 10% but it made no difference.
>
> My client server is NT, with SQL v7.0, TSM SQL client level 2.2.1
>
> Anyone any ideas?