Kevin,
This is a common misconception.
On startup Oracle determines the number of rollback
segments to bring on line based on the init.ora
parameters:
TRANSACTIONS / TRANSACTIONS_PER_ROLLBACK_SEGMENT
If the number of rollback segments specified by
ROLLBACK_SEGMENTS is less than that value, then Oracle
automatically will bring online any other PUBLIC
rollback segments to bring the total of online
rollback segments up to that value. Any PUBLIC
rollback segments remaining will be left offline.
PRIVATE rollback segments will only be brought online
automatically if specified in the ROLLBACK_SEGMENTS
parameter.
Misconception #2: TRANSACTIONS_PER_ROLLBACK_SEGMENT
determines the number of concurrent transactions that
can use a rollback segment. Granted that's what the
name implies, but this isn't the case. This parameter
is used only to determine the number of PUBLIC
rollback segments to bring on line automatically at
startup. The number of concurrent transactions that
can use a rollback segment is based on many factors,
the most important one being DB_BLOCK_SIZE.
I recommend using private rollback segments and
specifying them in ROLLBACK_SEGMENTS because it makes
it much easier to handle rollback segment problems.
If there's a problem with a rollback segment on
startup, for example, simply removing the segment from
the init.ora will usually allow you to at least get
the db open.
HTH,
-- Anita
--- Kevin Kostyszyn <[EMAIL PROTECTED]> wrote:
> Hi all,
> This brings me to a stupid question then. What is
> the true difference
> between a public and a private rollback segment?
> Because if I just think
> about it like a normal human being I would think
> that if a user made a
> Private rollback segment then only that user could
> use it, but of course I
> know that can't be the case.
> Kev
>
> -----Original Message-----
> Sent: Wednesday, May 09, 2001 10:26 AM
> To: Multiple recipients of list ORACLE-L
>
>
>
> Nixon,
>
> While SET TRANSACTION can be used to assign a
> rollback
> segment to a transaction, it cannot be assigned
> exclusively to
> that transaction as you have found.
>
> The ability to assign a rollback segment to a
> transaction and
> make it read-only for all others is something I've
> wanted myself
> for many years, and I know it's been on the official
> 'wish list' of
> requested changes by IOUG for some time.
>
> Maybe 9i? Anyone know?
>
> Jared
>
>
> On Wednesday 09 May 2001 01:40,
> [EMAIL PROTECTED] wrote:
> > Hi All,
> >
> > Here is my environment;
> >
> > NT v4
> > Db Oracle Workgroup v8.1.6
> >
> > Rollback Segments
> > SEGMENT_NAME OWNER
> TABLESPACE_NAME
> > ------------------------------ ------
> ------------------------------
> > SYSTEM SYS SYSTEM
> > RBS0 PUBLIC RBS
> > RBS_P1 SYS RBS
> > RBS_P2 SYS RBS
> > RBS_P3 SYS RBS
> > RBS_P4 SYS RBS
> > RBS_P5 SYS RBS
> >
> >
> > Is it possible to assign one public rollback
> segment explicitly to one
> > particular transaction? I tried using SET
> TRANSACTION USE ROLLBACK SEGMENT
> > but other users I found out can still use it. So,
> I guess the best
> > alternative is to set that RB segment to OFFLINE
> after using and set
> ONLINE
> > before executing the SET TRANSACTION ... Do you
> know how it can be done
> > inside Forms?
> >
> > Thanks in advance!
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