Re: rollback segments question

Maria wrote:

>Daniel Morgan <damorgan_at_x.washington.edu> wrote in message news:<1067277164.536028_at_yasure>...
>
>
>>Maria wrote:
>>
>>
>>
>>>Hello all
>>>
>>>I have 2 oracle database servers verion 8.1.7.4 on solaris 5.8, which
>>>I have the following rollback segements created:
>>>
>>>1) server #1
>>>"create public rollback segment RBS15
>>>tablespace RBS_TBS
>>>storage (initial 80000K next 80000K optimal 1700000K MINEXTENTS 20
>>>MAXEXTENTS 32765)"
>>>
>>>
>>>
>>>
>>>2) server #2
>>>"create public rollback segment RBS20
>>>tablespace RBS_TBS
>>>storage (initial 40000K next 40000K optimal 80000K MINEXTENTS 20
>>>MAXEXTENTS 32765K)"
>>>
>>>The tablespace is for #1 50GB and #2 40GB, my question is why is the
>>>tablespace for the bigger rollback showing only 2% used while for the
>>>smaller rollbacks is show 15% used. It should be the other way around
>>>?
>>>Can any one please help with this
>>>
>>>Regards
>>>Maria
>>>
>>>
>>>
>>>
>>Because that is how much they were used. The better question would be
>>why, in spite of
>>advice from industry experts such as Tom Kyte, are you using different
>>sizings on your
>>rollback segments and why, in spite of advice from industry experts not
>>to are you using
>>OPTIMAL.
>>
>>What you have here is a recipe for ORA-01555.
>>
>>
>
>I was getting the ORA-01555 ROLLBACK too small too old
>that is when I re created them double of size, should I NOT be using
>OPTIMAL size then ?
>Thank you
>Maria
>
>

First thing you should do is read the archives here in the usenet groups and the advice from Tom
Kyte at http://asktom.oracle.com. But to repeat it:

1. All rollback segments should be identically sized and sized large enough to handle your largest transation.
2. Optimal accomplishes nothing but for add overhead to the database. If you want a large rollback segment allocation either reset the segment size or the minimum extents.

-- 
Daniel Morgan
http://www.outreach.washington.edu/ext/certificates/oad/oad_crs.asp
http://www.outreach.washington.edu/ext/certificates/aoa/aoa_crs.asp
damorgan_at_x.washington.edu
(replace 'x' with a 'u' to reply)