Questions on extents, etc.

From: <argosy22_at_my-deja.com>
Date: 2000/04/20
Message-ID: <8dliqa$rqh$1@nnrp1.deja.com>#1/1

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

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Before you buy. Received on Thu Apr 20 2000 - 00:00:00 CDT