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Hi all,
I just noticed that no rollback_segment specified in my ini.ora file. Does that mean next time when db startup, all rollback_segment won't be online (execept system rbs)?
I have startup DB several times already, and everytime rbs are all online. - confused now.
thanks in advance
if the rollback segments are PUBLIC then they will come online. Only for PRIVATE rollbacks you need to list them in the init file.
- Rajeev
When the RBS are created as default like now in 8 version RBS01 .. RBS20 are created by default, and if you are using the same, then you dont have to specify in your INIT.ora .
Probably that's what is happening.
If you don't have any rollback segs specified in your init.ora, Oracle will calculate the number of RB segments it needs based on the following formula: number_of_RB_to_put_online = TRANSACTIONS/
TRANSACTIONS_PER_ROLLBACK_SEGMENT. If you have this number of RB segments created it will bring all online. If you have more than this number of RB segments it will left the others in offline mode.
AFAIK public and private RB segments are relevant only in Paralel Server environment. In normal configuration they behave exactly the same and the type of RB segment does not have any influence in the decision if system will bring the RB online or not.Quote:
Originally posted by rsuri
if the rollback segments are PUBLIC then they will come online. Only for PRIVATE rollbacks you need to list them in the init file.
When rollblck_segments rbs_01 created,
CREATE ROLLBACK SEGMENT rbs_01
TABLESPACE
STORAGE (INITIAL 10k NEXT 10k MINEXTENTS 2);
how to make it public or priv. during creation of rbs
20 rbs of my are public- if I don't specific when creating them, they are public. and acoording the formula, some will be online automatically. CORRECT!
I am not sure about the formula, But when you are creating the rollback segments you have to specify the PUBLIC in
create syntax,
Other whys the rollback segment will be created as private.
(On my knowledge).
Hi Jmodic,
You are saying that :
If you don't have any rollback segs specified in your init.ora, Oracle will calculate the number of RB segments it needs based on the following formula: number_of_RB_to_put_online = TRANSACTIONS/
TRANSACTIONS_PER_ROLLBACK_SEGMENT
From where Oracle is going to get both the parameters.
Pls. elaborate.
Those are initialisation parameters. You might have them specified in the initSID.ora. If you don't specify them there oracle will assign some default values to them during startup. To check what values have been assigned to them in your instance, run the following:
SELECT name, value FROM v$parameter
WHERE UPPER(name) IN ('TRANSACTIONS', 'TRANSACTIONS_PER_ROLLBACK_SEGMENT');
HTH,
Dear Jmodic, 10th May 2001 16:34 hrs chennai
As you have said fine i queried the v$parameter it shows as follows.
NAME VALUE
---------------------------------------------------------------- ------
transactions 75
transactions_per_rollback_segment 5
So i should have 15 RBS ? but my query reads as follows
SQL> select * from v$rollname;
USN NAME
---------- ---------------------
0 SYSTEM
1 RBS0
2 RBS1
3 RBS2
4 RBS3
5 RBS4
6 RBS5
7 RBS6
Note :In My init.ora RBS related parameters has been disabled.
# If using private rollback segments, place lines of the following
# form in each of your instance-specific init.ora files:
#rollback_segments = ( RBS0, RBS1, RBS2, RBS3, RBS4, RBS5, RBS6 )
# If using public rollback segments, define how many
# rollback segments each instance will pick up, using the formula
# # of rollback segments = transactions / transactions_per_rollback_segment
# In this example each instance will grab 40/5 = 8
# transactions = 40
# transactions_per_rollback_segment = 5
Cheers
Padmam
Padmam,
In your case Oracle will try to put 15 RBS online. But if you have only 7 RBS (RBS0..RBS6, SYSTEM RBS is not counted in the above formula) it will only bring all of those 7 RBS online. It will not complain or wite any messaage to alert file or anything.
If you now create additional 13 rollback segments and restart the database, Oracle will put the first 15 RBS online and leave the remaining 5 offline.
The commented text in the template of the init.ora refers only to Paralel Server configuration, it is irrelevant for single-instance configurations.
Hi Jmodic 10th May 2001 17:16 hrs chennai
I understand about Public RBS used for parallel server (multiple instances can share the same RBS) use.
1)But what i wanted to know is where to know that by default Number of RBS value from Views for a instance.
2)Then what is the use of then oracle giving private RBS as
rollback_segments = ( RBS0, RBS1, RBS2, RBS3, RBS4, RBS5, RBS6 ) at init.ora .which is going to automatically brings the RBS online.
So was step 1 default alocation based on default values 75/5 it allocates is the feature of 8i.?
Cheers
Padmam
I'm not sure I understand your question. If you dont have RBS specified in your init.ora and wan't to know how many RBS oracle will bring online and your instance is not started yet, you have two options:Quote:
Originally posted by padmam
1)But what i wanted to know is where to know that by default Number of RBS value from Views for a instance.
a) specify TRANSACTIONS and TRANSACTIONS_PER_ROLLBACK_SEGMENT in your init.ora and calculate the resulting number
b) find out the default values for this two parameters for your release/platform and again calculate the resulting number
If your database is allready started and wan't to know how many RBS was brought online initialy, check the V$PARAMETER for thos etwo parameters.
Remember that init.ora that is created during the initial database creation is only a template, which you are free to modify. The comented lines you are refering to are in there only as a reminder and are ment for Paralele Server only, although the comments are rather poor and insufficient. Note also that the content of the supplied init.ora is different for different releases and different platforms.Quote:
2)Then what is the use of then oracle giving private RBS as
rollback_segments = ( RBS0, RBS1, RBS2, RBS3, RBS4, RBS5, RBS6 ) at init.ora .which is going to automatically brings the RBS online.
No, AFAIK this is not new feature of 8i, it has been so at least since Oracle7.Quote:
So was step 1 default alocation based on default values 75/5 it allocates is the feature of 8i.?
Hi Jmodic, 10th May 2001 18:06 hrs chennai
I thought that there may be some kind of way to find out
the max default RBS.
Thanks Jmodic.
Cheers
Padmam
I wouldnt use 100% public RBS for OPS, had a bad experience when I was working with one senior dba