Re: Questions on extents, etc.

HI,

Thanks for responding.

So in this example, even though the tablespace is 25M, less than 15M are being used by the 3 rollback segments. So, about 10 megs are not utilized.

You say the MAXEXTENTS in the tablespace, puts a secondary limit on the rollback segments. Say I instead create each rollback segment to have 100 extents. Then each rollback segment is the same max size as the tablespace.

Would those rollback segments eventually conflict with each other, running out of room in the tablespace. That is, given a 3 or more big batch jobs running at once.

I'm wondering if I have to consider the sizing of both tablespaces and rollback segments when I am creating them?

Thanks,

Argosy

In article <%xuL4.2131$pQ1.31833_at_news.swbell.net>,   "spencer" <spencerp_at_swbell.net> wrote:
> if these three rollback segments are the only objects created in
> the tablespace, the maximum amount of storage that will be
> allocated within the tablespace is
> 3 * ( 30 * 160K) = 14400K
>
> + one oracle block (blocksized not known) for each datafile
> <= 64K )
>
> = 14464K = 14.125 megabytes
>
> the MAXEXTENTS parameter of each rollback segment is what limits
> the space allocated to each rollback segment.
>
> the MAXEXTENTS parameter on the tablespace is a default value
> applied to any object (e.g. a rollback segment) created in the
> tablespace that does not have a MAXEXTENTS value specified in
> the create statement.
>
> hth
>
> <argosy22_at_my-deja.com> wrote in message
> news:8dliqa$rqh$1_at_nnrp1.deja.com...
> > HI all,
> >
> > I've been reading about tablespaces, rollback segments,
> > extents, and I have some questions about them.
> >
> > If I use this statement to create a tablespace:
> >
> > Create tablespace ROLLBACK_TBS
> > DATAFILE '/rollback/somefile.dbf'
> > SIZE 25M
> > DEFAULT STORAGE
> > (
> > INITIAL 160K
> > NEXT 160K
> > PCTINCREASE 0
> > MINEXTENTS 2
> > MAXEXTENTS 100
> > )
> >
> > and then 3 rollback segments with this statement:
> >
> > Create ROLLBACK SEGMENT roll1_rbs
> > (roll2_rbs, roll3_rbs)
> > TABLESPACE ROLLBACK_TBS
> > STORAGE
> > (
> > INITIAL 160K
> > NEXT 160K
> > MINEXTENTS 2
> > MAXEXTENTS 30
> > )
> >
> >
> > I'm wondering:
> > - is the whole tablespace being used, or, am I limiting
> > its use to 16 megs (160k * 100 = 16000K = 16M) ?
> > If so, can we ensure all the 25M is used by just leaving
> > out the MAXEXTENTS clause?
> >
> > - is any transaction using this tablespace/rollback segment
> > now limited to 4800K (160K * 30 = 4800K = 4.8M) total rollback
> > resource? One big transaction can only use one rollback
> > segment, correct?
> >
> > - can I create 10 rollback segments, in the same manner,
> > all using the same tablespace, or will that cause an error?
> > (10 * 4.8M = 48M. Larger than 25M.)
> >
> > - if a transaction runs out of extents, could I just increase
> > the rollback segment's MAXEXTENTS to say, 100? Would this
> > conflict with the other rollback segments?
> >
> > - while not a good idea to just give the UNLIMITED clause
> > for rollback segments, if it was given, does the rollback
> > segment grow until the tablespace reaches 25M? Or, until the
> > disk is full?
> >
> >
> > I've read what I could on these subjects, but it's not
> > quite clear yet (as you can tell).
> >
> > Thanks,
> >
> > Argosy
> >
> >
> >
> >
> >
> >
> > Sent via Deja.com http://www.deja.com/
> > Before you buy.
> >
> >
>
>

Sent via Deja.com http://www.deja.com/
Before you buy. Received on Thu Apr 20 2000 - 00:00:00 CDT