Nested Transactions - what for?

Hi
Can someone explain what nested transactions can be used for? I know about
the outer an inner transaction but you still either commit or rollback all
transactions.
In Oracle you can start autonomous transaction within another transaction
and any commit or rollback statement affects its own transaction.
So - I am not looking at explanation how to create nested transactions but
what could be a practical use of them?I think that this is largely a leftover from the original Sybase design.
As you know, there are no nested transactions in SQL Server, semantically speaking.
Why did they put in the syntax then? I guess you had to be in that Sybase design meeting to be able
to answer that question. My guess is that it allow for code modules to call each other. One stored
proc programmer want to transaction-protect the code. The proc he is writing will call another proc
which is also transaction-protected. Stuff like that...
Note that savepoint is another matter. This gives the ability to perform partial rollbacks. This is
IMO much more useful then doing partial commits. I find the thought of a partial commit a bit scary,
but perhaps this is because the feature isn't available in SQL Server.
One scenario I would consider it useful, though, is when you want to log actions even if you
rollback the transaction. In SQL Server 2000, we can often achieve the same functionality logging to
a table variable (which survives a ROLLBACK).
--
Tibor Karaszi, SQL Server MVP
http://www.karaszi.com/sqlserver/default.asp
http://www.solidqualitylearning.com/
"Witold" <witoldi@.shaw.ca> wrote in message news:bWo8d.211357$%S.80172@.pd7tw2no...
> Hi
> Can someone explain what nested transactions can be used for? I know about
> the outer an inner transaction but you still either commit or rollback all
> transactions.
> In Oracle you can start autonomous transaction within another transaction
> and any commit or rollback statement affects its own transaction.
> So - I am not looking at explanation how to create nested transactions but
> what could be a practical use of them?
>