Re: Newbie ?: Rollback Segments and the High Water Mark

Hi Verna,

An attempt to resolve the confusion:
The SYSTEM rollback segment is used for DDL transactions only (ie CREATE an object, DROP an object etc). It is normally not used for ordinary transactions.
A larger transaction will force Oracle to allocate extra extents in the rollback segment. This increases the HWM. Unless you set OPTIMAL for each rollback segment (which I personally never do), once the transaction has been committed, the space will not be deallocated, it is however 'free' to be used by another transaction. If you set OPTIMAL Oracle will trim down the rollback segment. However later on it probably is extended again. That's something I want to avoid in my systems.
If your rollback segments R01-R04 are not online, this means they are private rollback segments. You should name them in the init<sid>.ora file with the following line
rollback_segments = (r01, r02, r03, r04)

and they will be online automatically after startup.

Hth,

Sybrand Bakker, Oracle DBA

On Sat, 2 Oct 1999 21:49:13 -0700, "Verna Legaspi" <vlegaspi_at_uswest.net> wrote:

>I'm a bit confused. When I start the database, only the SYSTEM RBS is
>online. Using storage manager to see if I have any potential free space
>problems. SYSTEM RBS is pretty much at the "end" of the High Water Mark.
>(Please excuse my terminology if I'm using them incorrectly.)
>
>So, I bring online r01 - r04. Why, all of a sudden, are the high water
>marks at the end of each RBS? Doesn't the High Water Mark being at the
>"end" designate that the segment is "full?"
>
>TIA
>
>
Received on Sun Oct 03 1999 - 06:43:44 CDT