Re: Questions on extents, etc.

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.
>
>
Received on Wed Apr 19 2000 - 00:00:00 CDT