Rollback segment + oracle 8i

Hi,
I am working in oracle 8i. I am having a doubt in rollback segment. what is the use of optimal parameter in rollback segment and whether its important or not.
Rgds...

This might help:
http://download-west.oracle.com/docs/cd/A87860_01/doc/server.817/a76956/rollbak.htm#586

Similar Messages

Error while creating the rollback segment (Oracle 8i & OS Win NT)

hi
I am using Oracle 8i and when i am creating the new rollback segment for my database i have got following error message
ORA-01593 Rollback segment optimal size (30 blks) is smaller than the computed initial size (2560 blks)
CREATE ROLLBACK SEGMENT "RBS11" TABLESPACE "RBS1"
STORAGE ( INITIAL 120K NEXT
120K OPTIMAL
240K MINEXTENTS 2
MAXEXTENTS 100)
Note:- db_block size is 8k
Tablespace RBS1 is the Locally managed Tablespace having datafile of 50m and uniform size of 10m
But Given statement processed while i am using Tablespace RBS (winch is data dictionary managed)
Plz, suggest me to cause of that error and solution

You said 120K optimal and initial is 120K with minextents of 2. The optimal size then will be smaller than the initial allocation for the rbs.
ORA-01593: rollback segment optimal size (string blks) is smaller than the computed initial size (string blks)
Cause: Specified OPTIMAL size is smaller than the cumulative size of the initial extents during create rollback segment.
Action: Specify a larger OPTIMAL size.

ROLLBACK SEGMENT의 MINEXTENTS를 20 이상으로 하면 좋은 이유

제품 : ORACLE SERVER
작성날짜 : 2003-06-19
ROLLBACK SEGMENT의 MINEXTENTS를 20 이상으로 하면 좋은 이유
=========================================================
PURPOSE
이 자료는 다음과 같은 주제에 대하여 소개하는 자료이다.
이 문서는 database application의 요구 사항을 충족시키기 위해 고려되어
져야 할 rollback segment tablespace 구성에 관한 내용을 담고 있다.
Creating, Optimizing, and Understanding Rollback Segments
-Rollback Segment 구성과 기록 방식
-Transaction에 Rollback Segment를 할당하는 Oracle 내부 메커니즘
-Rollback Segment 크기와 갯수
-Rollback Segment의 크기와 갯수 결정을 위한 테스트
-Rollback Segment extent의 크기와 갯수
-Rollback Segment의 minextents를 20 이상으로 하면 좋은 이유?
-Rollback Segment의 Optimal storage parameter와 Shrink
Explanation
Rollback Segment 구성과 기록 방식
Rollback segment는 extent라 불리는 연속적인 여러 개의 block으로 구성된다.
Rollback segment는 ordered circular 방식으로 extent를 쓰게 되는데,
current extent가 full이 되면 next extent로 옮겨 가며 사용하게 된다.
Transaction은 rollback segment 내의 current location에 record를 쓴 다음,
record의 size 만큼 current pointer를 옮겨 간다.
Rollback segment에 현재 record가 쓰여지고 있는 위치를 "Head"라고 한다.
또한, "Tail"이란 용어는 rollback segment에서 가장 오래된 active
transaction record의 시작 위치가 되는 부분을 말한다.
Transaction에 Rollback Segment를 할당하는 Oracle 내부 메커니즘
새로운 transaction이 rollback segment 를 요청하면, 각 rollback segment
를 이용하고 있는 active transaction 갯수를 확인하여 가장 적은 갯수의
active transaction 을 가진 rollback segment를 할당하게 된다.
Rollback segment는 transaction load를 처리하기에 충분한 크기를 가져야
하고, 필요한 만큼의 rollback segment를 사용할 수 있도록 적당한 갯수의
rollback segment를 가져야 한다.
1. 한 transaction은 단 하나의 rollback segment만을 사용할 수 있다.
2. 같은 extent에 여러 transaction이 기록할 수 있다.
3. Rollback segment의 Head는 Tail에 의해 현재 사용 중인 extent를
침범하지 않는다.
4. 링 형태로 구성되어 있는 rollback segment의 extent들은 다음 extent를
찾을 때 절대 건너 뛰는 일이 없으며, 순서를 뒤바꾸어 사용하지도 않는다.
5. Head가 next extent를 찾지 못하면, 새로운 extent를 추가로 할당하고,
그 extent를 링 안에 포함시킨다.
위와 같은 원리를 감안할 때, transaction size 뿐만 아니라 transaction
time도 상당히 중요한 고려 사항이라는 것을 알 수 있다.
Rollback Segment 크기와 갯수
Rollback segment size가 충분한지 판단하는 기준은 transaction activity에
직접적으로 영향을 받는다. 주로 일어나는 transaction activity에 근거하여
rollback segment size를 결정하여야 하고, 잘 일어나지 않는 특수한 경우의
큰 transaction이 문제라면 별도의 rollback segment로 관리되어야 한다.
Transaction 발생 중 Head가 너무 빨리 wrap around 시켜서 tail을 catch하
지 않도록 하여야 하며, 자주 변경되는 data에 대해 long-running query가
수행되었을 경우 read-consistency가 유지될 수 있도록 rollback segment
가 wrap around되지 않아야 한다.
Rollback segment 갯수를 적당히 잡아야 하는 이유는 process들 간에
contention을 방지하기 위함이고, V$WAITSTAT, V$ROLLSTAT, V$ROLLNAME
view를 통해서 contention을 확인할 수 있으며, 조회문은 다음과 같다.
sqlplus system/manager
select rn.name, (rs.waits/rs.gets) rbs_header_wait_ratio
from v$rollstat rs, v$rollname rn
where rs.usn = rn.usn
order by 1;
위의 query에 의해 조회된 rbs_header_wait_ratio 가 0.01 보다 크면,
rollback segment 갯수를 추가한다.
Rollback Segment의 크기와 갯수 결정을 위한 테스트
1. Rollback segment tablespace 생성
2. 테스트하기 위해 생성할 Rollback segment 갯수 결정
3. 같은 크기의 extent로 rollback segment 생성
extent 갯수는 최대 확장 시 10 - 30 개 정도가 되도록 extent 크기를 결정
4. Rollback segment의 minextents는 2이다.
5. 테스트할 rollback segment와 system rollback segment만 online 상태로 한다.
6. Transaction을 수행하고, 필요하면 application을 load한다.
7. Rollback segment contention을 확인한다.
8. Rollback segment가 최대 얼마까지 확장하는지 모니터링한다.
Rollback Segment extent의 크기와 갯수
Rollback segment가 자라나는 최대 사이즈를 알 수 있는데, 이 수치를
"minimum coverage size"라 한다. 만약, contention이 발생한다면 rollback
segment 갯수를 늘려 가면 테스트를 반복한다. 또한, extent 갯수가 10개
미만이나 30개 이상이 될 필요가 있다면 extent 크기를 늘리거나 줄이면서
테스트를 반복해 나가면 된다.
Rollback segment의 extent 크기를 정할 때, 각 extent는 모두 같은 크기로
생성할 것을 recommend한다.
Rollback tablespace의 크기는 extent size의 배수로 지정한다.
최적의 성능을 위한 rollback segment의 minextents는 20 이상이어야 한다.
Rollback Segment의 minextents를 20 이상으로 하면 좋은 이유?
Rollback segment는 dynamic하게 allocate되고, 더 이상 필요 없게 되었을 때
(만약, Optimal parameter가 셋팅되어 있으면) 모두 commit된 extent에
대해서는 optimal size 만큼만 남기고 release(deallocate)된다.
Rollback segment가 적은 수의 extent를 가질 수록, space 할당/해제 시
extent 수가 많을 때보다 큰 사이즈의 space가 할당되고, 해제된다.
다음과 같은 예를 들어 보자.
200M 정도의 rollback segment가 있는데, 100M 짜리 2개의 extent로 이루어져
있다고 가정해보자. 이 rollback segment에 추가로 space를 할당해야 할 일이
생겼을 때, 모든 rollback segment extent는 같은 크기를 가져야 한다는 점을
감안할 때, 100M 짜리 extent를 하나 더 할당해야 할 것이다.
이 결과 직전의 rollback segment 크기에 비하여 50% 만큼의 크기 증가분이
생겨나게 된 것인데, 실제 필요로 하는 space보다 더 많은 space가 할당되었을
것이다.
이와 반대로, 10M 짜리 extent 20개로 구성된 200M 짜리 rollback segment를
생각해보자.
여기에 추가로 space를 할당해야 할 일이 생겼을 때, 10M 짜리 extent 하나만
추가되면 되는 것이다.
Rollback segment가 20개 또는 그 이상의 extent로 구성되어 있다면 extent가
하나 더 증가할 경우가 생겼을 때, rollback segment의 전체 크기가 5% 이상은
늘어나지 않는다는 것이다.
즉, space의 할당과 해제 작업이 보다 유연하고 쉽게 일어날 수 있다.
요약하면, rollback segment의 extent 갯수를 20 이상으로 잡으면 space
할당과 해제가 "보다" 수월해진다.
실제로 extent 갯수를 20 이상으로 잡았을 때, 처리 속도가 훨씬 빨라진다는
사실이 많은 테스트 결과 밝혀졌다.
한가지 확실한 사실은, space를 할당하고 해제하는 작업은 cost가 적게 드는
작업이 아니라는 사실이다.
실제로 extent가 할당/해제되는 작업이 일어날 때, performance가 저하되는
일이 발생한다는 것이다.
Extent 하나에 대한 cost는 별 문제가 안 된다고 할지라도, rollback segment
는 끊임없이 space를 할당하고 해제하는 작업을 반복하기 때문에 작은 크기의
extent를 갖는 것이 cost 측면에서 훨씬 효율적이라는 결론이다.
Rollback Segment의 Optimal storage parameter와 Shrink
Optimal은 deallocate 시에 rollback segment 내에 optimal size 만큼의
extents를 유지하기 위해 사용하는 rollback segment storage parameter이다.
다음과 같은 명령으로 사용한다.
alter rollback segment r01 storage (optimal 1m);Optimal size는 storage 절 안에서 기술되어야 한다.
Optimal size 이상이 되면, 모두 commit된 extent에 대해서는 optimal size
만큼만 남기고 release된다.
즉, optimal에서 지정한 크기 만큼만 rollback segment를 유지하겠다는
뜻이며, 일정한 크기로 늘어났다가 다음번 tx이 해당 rbs를 취할 경우
optimal size만큼 resize하는 option이다.
rbs의 가장 최근에 사용된 extent가 다 차서 다른 extent를 요구할 때
이 optimal size와 rbs size를 비교하게 되며, 만약 rbs size가 더 크다면
active tx에 관여하지 않는 tail extent에 대하여 deallocation이 이루어진다.
특정 rollback segment가 너무 큰 space를 차지해서 다른 rollback segment가
extent를 발생할 수 있는 여유 공간을 부족하게 만들기 때문에 이를 극복하기
위해서 optimal size를 지정할 필요가 있다.
즉, optimal parameter를 지정하면 space availability 측면에서 효율적이다.
다음과 같이 shrink 명령을 수행하는데, size를 지정하지 않으면 optimal
size 만큼 shrink된다.
alter rollback segment [rbs_name] shrink to [size];Shrink 명령 수행 후, 바로 줄어들지 않는 경우가 있는데,
transaction이 있는 경우는 줄어들지 않고, transaction이 종료되면 줄어든다.
Optimal이 적용되는 시간은 session이 빠져 나가고 약 5~10 분 정도 걸린다.
적당한 OPTIMAL SIZE?
=> 20 ~ 30 extents 정도가 적당한데, batch job의 성격에 따라 size는 달라
지며 각 optimal의 합이 datafile의 size를 넘어도 전혀 상관없다.
Optimal size를 initial, next와 같게 주면 extent가 발생하는 매번 shrink가
일어나므로 좋지 않다.
RBS들의 평균 크기를 구하여 이것을 optimal 크기로 지정하여 사용하는 것을
권한다.
다음의 query를 이용하여 peak time에 rollback segment들의 평균 크기를 구한다.
select initial_extent + next_extent * (extents-1) "Rollback_size", extents
from dba_segments
where segment_type ='ROLLBACK';
이 크기의 평균값(bytes)을 rollback segment들의 optimal size로 사용할 수
있다.
주의할 사항은 너무 자주 shrink된다거나 optimal 값을 너무 작게 주면
ora-1555 : snapshot too old error가 발생할 확률이 높아지므로,
사용하지 않는 것이 좋을 수도 있고, 되도록 큰 값으로 셋팅해야 한다.
Rollback segment의 optimal size를 확인할 수 있는 view는 V$ROLLSTAT
이라는 dynamic view로서 OPTSIZE column에서 확인이 가능하다.
Example
none
Reference Documents
<Note:69464.1>

Transaction table in rollback segments

hi guys,
I have read the following, but am still having a little difficulty conceptualising. Would someone be kind enough to give me a very brief example?
thanks
For each rollback segment, Oracle maintains a transaction table--a list of all transactions that use the associated rollback segment and the rollback entries for each change performed by these transactions.

First of all, the statement is talking about old manual undo management using rollback segment.
If you check the preceding two paragraph of the statement then it's easier to understand,
It basically says, Rollback segment hold rollback entries of transaction. To make it easier to track transactions and undo entries, Oracle maintain a table to save such info.
Rollback segment , transaction and undo entries are one to many relationships.
Rollback Segment --< Transactions --< Undo Entries
http://download.oracle.com/docs/cd/B10501_01/server.920/a96524/b_deprec.htm
Contents of a Rollback Segment
Information in a rollback segment consists of several rollback entries. Among other information, a rollback entry includes block information (the file number and block ID corresponding to the data that was changed) and the data as it existed before an operation in a transaction. Oracle links rollback entries for the same transaction, so the entries can be found easily if necessary for transaction rollback.
Neither database users nor administrators can access or read rollback segments. Only Oracle can write to or read them. (They are owned by the user SYS, no matter which user creates them.)
How Rollback Entries Are Logged
Rollback entries change data blocks in the rollback segment, and Oracle records all changes to data blocks, including rollback entries, in the redo log. This second recording of the rollback information is very important for active transactions (not yet committed or rolled back) at the time of a system crash. If a system crash occurs, then Oracle automatically restores the rollback segment information, including the rollback entries for active transactions, as part of instance or media recovery. When recovery is complete, Oracle performs the actual rollbacks of transactions that had been neither committed nor rolled back at the time of the system crash.
When Rollback Information Is Required
For each rollback segment, Oracle maintains a transaction table--a list of all transactions that use the associated rollback segment and the rollback entries for each change performed by these transactions. Oracle uses the rollback entries in a rollback segment to perform a transaction rollback and to create read-consistent results for queries.

How to check/find the size of current ROLLBACK segment in oracle 10g

How to check/find the size of current ROLLBACK segment in oracle 10g ? Kindly help

A rollback segment name like "_SYSSMU231$" is used when you have Automatic Undo Management enabled.
The only relevant parameters are :
1. UNDO_MANAGEMENT=AUTO
2. UNDO_RETENTION=n minutes ==> this is what everyone should be interested in
3. The sizes of the Undo Tablespace datafiles and whether AUTOEXTEND is ON or OFF
No one should be interested in the size of a single undo segment when Automatic Undo Management is enabled.
Possible causes of ORA-01555 errors in Automatic Undo Management
a. UNDO_RETENTION is too low
b. Undo tablespace is too small
Hemant K Chitale

Not able to see rollback segment in oracle 10g

hi all
I created rollback segment by using command
CREATE ROLLBACK SEGMENT rs1 TABLESPACE rbs_ts
and made it online but not able to see
segment name by using
select * from dba_rollback_segs
Please help me
Ragards
Edited by: 174313 on Dec 1, 2008 3:19 PM

You can start with the following links in 10g documentation.
http://download.oracle.com/docs/cd/B19306_01/server.102/b14220/mgmt_db.htm#sthref2230
http://download.oracle.com/docs/cd/B19306_01/server.102/b14220/logical.htm#CHDGJJEJ
http://download.oracle.com/docs/cd/B19306_01/server.102/b14220/logical.htm#CNCPT305

Oracle 9i - Rollback Segment Needs Recovery

I have been noticing for a few days that my UNDO tablespace has been growing in size for no apparent reason. My datafiles have only increased by 400 Meg over last 4 days, but UNDO tablespace has grown from 100 Meg - 5.6 Gig....
I decided to create a new UNDO tablespace and drop the old one.....
I created a new tablespace, changed the UNDO configuration to point to new tablespace and bounced the instance. The instance came back up fine, using the new UNDO tablespace....I then went to take the old tablespace offline and drop it....It went offline fine, but when I went to remove it, I received an Oracle error saying tablespaces was using rollback segment _SYSSMU24$.....
I looked in the alert log and I'm getting a message:
SMON: about to recover undo segment 24
SMON: mark undo segment 24 as needs recovery
When I query the dba_rollback_segs table, it shows that all rollback segments prior to _SYSSMU24$ are online, 24 & 25 are listed as NEEDS RECOVERY, and all others below that are offline....
Any help on resolving this issue would be appreciated....

Metalink overrides any thing said, adviced, or written in this forum, if you have already opened a Service Request, as suggested by Daniel Morgan.
Just in case this may be helpful to you or others facing a similar situation, I suggest you to check this case Re: Error while Droping Undo Tablespace.
Make sure you have a full useful database backup as well as the required archive log files.
~ Madrid

Rollback segment corruption on oracle 7.3

We have an oracle 7.3 database on solaris(sparc) 2.6.
In the midddle of the transactions, the following error message occured:
ORA 1578 Data block corrupted(file #2, block#8274)
ORA-1110 Datafile 2:'/user1/oradb/rbstbl.dbf'
(this datafile corresponds to the rollback segment table space).
Action Taken:
1. Tried to make the rollback segments offline, but out of 11, 2 rollback segments could not be taken offline. The status for these 2 was 'pending offline'.
2. Made the table space and datafile offline.
3. Created new rollback segments with new datafile and rollback segments, duly commenting the same in init.ora.
4. The status for these 2 rollback segments has now changed to 'needs recovery'. This status is preventing us from taking any further action.
We would like to drop the old table space.
We need you kind help in getting out of this loop!
Pls. mail your reply to [email protected]

Kathleen,
Sorry, the character set scanner only supports 8.0.6 and above. Can you first migrate your US7ACII database to 9.2, and run the scanner before changing database character set to WE8ISO8859P15? Also you can read this paper http://www.oracle.com/technology/tech/globalization/pdf/mwp.pdf
to understand why you may have invalid data in your US7ASCII database and the best way to migrate it. I am also wondering about your choice of P15 versus P1 and WIN1252? If you need further information you can contact me directly at [email protected]

OPTIMAL size for rollback segment in Oracle 8i

In our Database we have 13 Rollback segments & total size of all rollback segments is 33gb.
Used % it is showing 99.84%.
each rollback segment having near around 4gb of size.
I am in confusion to set OPTIMAL value for each rollback
segment.
can any one help me out reg this.
My roll back seg statistics are as fallows:
SEGMENT_NAME TABLESPACE_NAME WAITS SHRINKS WRAPS STATUS
R00 SYSTEM 0 0 12 ONLINE
RBS0 RBS 0 0 19 ONLINE
RBS01 RBS 0 0 16 ONLINE
RBS02 RBS 1 0 12 ONLINE
RBS03 RBS 0 0 11 ONLINE
RBS04 RBS 0 0 21 ONLINE
RBS05 RBS 1 0 22 ONLINE
RBS06 RBS 0 0 16 ONLINE
RBS07 RBS 0 0 15 ONLINE
RBS08 RBS 0 0 12 ONLINE
RBS09 RBS 1 0 19 ONLINE
SEGMENT_NAME TABLESPACE_NAME WAITS SHRINKS WRAPS STATUS
RBS12 RBS 0 0 13 ONLINE
RBS13 RBS 0 0 18 ONLINE
SYSTEM SYSTEM 0 0 0 ONLINE

Aman,
Definitely that would be a great approach to share the knowledge; but right now my notes are still in the shape of notes only; i have'nt tested them. I simply read forum and asktom and whenever i found good lines i copy and paste them and whenever i found the similar question in the forum i paste / repharase there in my own language and understanding (because till then i have tested and learnt them very well.)
Although i am highly obliged by your suggestation; let me that much knowledgable; so that i may run my own blog...!
Regards
Girish Sharma

Oracle error: Ora-01555 : snapshot too old: rollback segment number 1......

System Error: Unknown Database error (type qqdb_ResourceException) on WMS_WH1: Execute failed for SQL statement ............... error from database is: ORA-01555: snapshot too old: rollback segment number 1 with name "_SYSSMU1$" too small...
Any ideas ? Please help.
Thank you.

You either have
- an UNDO tablespace that is way too small (rollback segments that are too small); or
- an application that does way too many COMMITs (common with apps ported from SQL Server)
From the added info, I would guess that the Java program has a major loop and does processing on each of the values it gets in that loop. At the end of each turn in the loop, it does a commit. Then it tries to look at the next record in the master list. After a while (say around 388 loops ;-) ) it dies.
The reason is that when it looks for information in the master query, it needs to rebuild that information to the moment that query was initiated. It uses rollback (AKA undo) to rebuild that. But rollback is not guaranteed to exist after a commit (unless forced) and once a commit happens, that area can be reused. When it is reused, the information is no longer there to rebuild the row, and that raises an ORA-01555
Edited by: Hans Forbrich on Sep 11, 2009 3:44 PM

Forcing a specific rollback segment on a transaction does not seem to work

Hi!
We're using Oracle 9.2.0.5.0 on Sun Solaris and we're still configured to use Rollback Segments.
We have an issue with Snapshot too old due to RBS too small on a long query I attach below for reference:
set heading off
set pagesize 0
set feedback off
set linesize 200
<<<<< SET TRANSACTION USE ROLLBACK SEGMENT UMF_RBS_LARGE_TRAN; <<<<<
SELECT ucms_cards.msisdn
|| ';;' || to_char(to_date(substr(ucms_cards.notes,14+length(ucms_cards.msisdn),19),'MM-DD-YYYY.HH24-MI-SS'),'DD/MM/YYYY HH24:MI:SS')
|| ';;' || to_char(ucms_batches.expiry_date,'dd/mm/yyyy')
|| ';;' || ucms_cards.serial_no
|| ';;' || ucms_cards.serial_no
|| ';;' || ucms_cards.batch_serial_no
|| ';;' || ' '
|| ';;' || CASE ucms_cards.card_status
WHEN 'used' THEN '1'
ELSE '0'
END
|| ';;' || CASE WHEN date_booked_in is null THEN '01/01/1970 00:00:00' ELSE to_char(date_booked_in,'DD/MM/YYYY') || ' 00:00:00' END
|| ';;' || ' '
from ucms_batches,ucms_cards, UCMS_EVENT_LOG
WHERE ucms_cards.batch_serial_no = ucms_batches.serial_no
AND ucms_cards.serial_no = substr(UCMS_EVENT_LOG.ENTITY_ID,11,length(UCMS_EVENT_LOG.ENTITY_ID)-9)
AND UCMS_EVENT_LOG.PARTY_NO in (0)
AND UCMS_EVENT_LOG.TIMESTAMP>=TO_TIMESTAMP(TO_CHAR(SYSDATE-1, 'DD-MM-YYYY') || ' 00:00:01', 'DD-MM-YYYY HH24:MI:SS')
AND UCMS_EVENT_LOG.TIMESTAMP<=TO_TIMESTAMP(TO_CHAR(SYSDATE-1, 'DD-MM-YYYY') || ' 23:59:59', 'DD-MM-YYYY HH24:MI:SS')
AND UCMS_EVENT_LOG.USER_ID LIKE 'SCP-AGENT1%'
AND UCMS_EVENT_LOG.EVENT_TYPE_ID IN (1,2)
AND UCMS_EVENT_LOG.ENTITY_TYPE_ID LIKE 'ucms_cards%'
UNION
SELECT ucms_imported_cards.msisdn
|| ';;' || to_char(to_date(substr(ucms_imported_cards.notes,14+length(ucms_imported_cards.msisdn),19),'MM-DD-YYYY.HH24-MI-SS'),'DD/MM/YYYY H24:MI:SS')
|| ';;' || to_char(ucms_imported_cards.expiry_date,'dd/mm/yyyy')
|| ';;' || ucms_imported_cards.serial_no
|| ';;' || ucms_imported_cards.serial_no
|| ';;' || DBMS_UTILITY.GET_HASH_VALUE(ucms_imported_cards.card_type,1,65536)
|| ';;' || ' '
|| ';;' || CASE ucms_imported_cards.card_status
WHEN 'used' THEN '1'
ELSE '0'
END
|| ';;' || '01/01/1970 00:00:00'
|| ';;' || ' '
from ucms_imported_cards, UCMS_EVENT_LOG
where ucms_imported_cards.serial_no = substr(UCMS_EVENT_LOG.ENTITY_ID,11,length(UCMS_EVENT_LOG.ENTITY_ID)-9)
AND UCMS_EVENT_LOG.PARTY_NO in (0)
AND UCMS_EVENT_LOG.TIMESTAMP>=TO_TIMESTAMP(TO_CHAR(SYSDATE-1, 'DD-MM-YYYY') || ' 00:00:01', 'DD-MM-YYYY HH24:MI:SS')
AND UCMS_EVENT_LOG.TIMESTAMP<=TO_TIMESTAMP(TO_CHAR(SYSDATE-1, 'DD-MM-YYYY') || ' 23:59:59', 'DD-MM-YYYY HH24:MI:SS')
AND UCMS_EVENT_LOG.USER_ID LIKE 'SCP-AGENT1%'
AND UCMS_EVENT_LOG.EVENT_TYPE_ID LIKE '2%'
AND UCMS_EVENT_LOG.ENTITY_TYPE_ID LIKE 'ucms_imported_cards%';
As you see we forced the session to use a huge RBS created for the purpose, but strangely after a long while the query fails with a RBS too small failure due to another RBS, not the one specified.
Is there any chance the UNION or any other component of the query is implicitly opening a new transaction with a different RBS associated?
Any chance to force the same RBS specified explicitly?
Thanks!
Mike

albertone wrote:
but strangely after a long while the query fails with a RBS too small failure due to another RBS, not the one specified.You misunderstand snapshot too old. It can be caused by other sessions same as by your session. Assume AFTER your session issued select some other session modified one (or more) tables ucms_batches, ucms_cards, UCMS_EVENT_LOG and committed changes. By the time your select reaches to fetch rows modified by that other session rollback extents in rollback segment used by that other session were reused. You will get snapshot too old. Bottom line - all sessions modifying table(s) used by your select must use rollback segments large enough so they are not overwritten before corresponding rows are needed by your select.
SY.

Error rollback segment while exporting a table

I am getting error while exporting a table, can someone advise me how i can handle this issue.
EXP-00056: ORACLE error 1555 encountered
ORA-01555: snapshot too old: rollback segment number with name "" too small
ORA-22924: snapshot too old
Thanks

Hi, I have the same problem...
I have a table with a blob type (14740 records)
I have increase the PCTVERSION to 100 (= maximum)
undo_retention = 604800 (7 days)
undo tablespace = 2 Gb
exporting with parameter CONSISTENT=n
Still I got the message
EXP-00056: ORACLE error 1555 encountered
ORA-01555: snapshot too old: rollback segment number with name "" too small
ORA-22924: snapshot too old
When exporting the table
What do I have to do more ?????

Rollback segment is filling up during creation of the database

Hi
The Rollback segment is showing around 520mb immediately after
creation of the database after following the wizard provided in
the enterprise manager of oracle. What might be the reason. How
to reduce it. Could any one give me a solution for this matter.
Thanks in Advance.

I tried creating the password file using the following command:
orapwd file=/home/oracle/product/9.2.0/dbs/orapwHR.ora
password=HR entries=5
and got the same error:
ORA-01501 Create Database failed.
ORA-01990 -ERROR opening password file '/home/oracle/product/9.2.0/dbs/orapw'
ORA-27037 Unable to obtain file status.
Linux error: 2: No such file or directory.
Additional information: 3.
Does anybody know how to fix this problem?
Thanks,
Katya

How to get the size of rollback segments

Hi,
on which oracle table can I see which are the rollback segments and its own size?
Thanks!

doc questions like this one are best answered by querying the view DICT which is present in every release of Oracle (and which you of course -again- fail to mention)
Sybrand Bakker
Senior Oracle DBA

Trying to understand rollback segments - offline tblspaces for backup

Using Oracle 8i, on Windows platform - The question - receive an error ORA-01556 when performing a
sql "ALTER TABLESPACE MY_TBS_LT OFFLINE IMMEDIATE";
=============================================
First off I created a tablespace and table on an 8i database.
create tablespace my_tbs_lt_tbs_lt
datafile '&&2\oradata\&&1\my_tbs_lt_guitest1.dbf'
size 10M
AUTOEXTEND ON NEXT 1280k EXTENT MANAGEMENT LOCAL UNIFORM SIZE 128K; <===== Is this right for use with rollback segments?
CREATE ROLLBACK SEGMENT rbgui1t2 STORAGE(INITIAL 50K NEXT 250K)
tablespace my_tbs_lt;
CREATE ROLLBACK SEGMENT rbgui2t2 STORAGE(INITIAL 50K NEXT 250K)
tablespace my_tbs_lt;
CREATE ROLLBACK SEGMENT rbgui3t2 STORAGE(INITIAL 50K NEXT 250K)
tablespace my_tbs_lt;
CREATE ROLLBACK SEGMENT rbgui4t2 STORAGE(INITIAL 50K NEXT 250K)
tablespace my_tbs_lt;
-- Bring new rollback segments online
ALTER ROLLBACK SEGMENT rbgui1t2 ONLINE;
ALTER ROLLBACK SEGMENT rbgui2t2 ONLINE;
ALTER ROLLBACK SEGMENT rbgui3t2 ONLINE;
ALTER ROLLBACK SEGMENT rbgui4t2 ONLINE;
CREATE TABLE guitester.guitester_t2
( employee_id NUMBER(6)
, first_name VARCHAR2(20)
, last_name VARCHAR2(25)
CONSTRAINT emp_last_name_nn_demo NOT NULL
, email VARCHAR2(25)
CONSTRAINT emp_email_nn_demo NOT NULL
, phone_number VARCHAR2(20)
, hire_date DATE DEFAULT SYSDATE
CONSTRAINT emp_hire_date_nn_demo NOT NULL
, job_id VARCHAR2(10)
CONSTRAINT emp_job_nn_demo NOT NULL
, salary NUMBER(8,2)
CONSTRAINT emp_salary_nn_demo NOT NULL
, commission_pct NUMBER(2,2)
, manager_id NUMBER(6)
, department_id NUMBER(4)
, dn VARCHAR2(300)
, CONSTRAINT emp_salary_min_demo
CHECK (salary > 0)
tablespace my_tbs_lt;
=======================================
I changed the initSID.ora file to have
Rollback_segments=( rbgui1t2, rbgui2t2, rbgui3t2, rbgui4t2)
=======================================
restarted everything
========================================
did a backup of the tablespace my_tbs_lt;
========================================
added some data to the table in the tablespace
========================================
ran a restore/recover - Get the error
========================================
It makes sense that I get the error because it is the tablespace that I have been working with, adding data. Is my logic correct? How does one restore a tablespace if it has rollback segments active? Can someone look to make sure I am declaring the rollback segments appropriately?

Thank you for the link - very helpful.
So would a more appropriate scheme be:
Create a tablespace
Create rollback segments
Put them online
enter their names in the ROLLBACK_SEGMENTS= segment(s)
I havent read everything, so you may say go look at the link again, but a second question. If you are managing the extent locally, does it not use a rollback segments, or is it using system, or is it actually creating rollback segments for itself within the context of the local management?
In my above scenario, I would have to take my rollback segment offline as well as the tablespace.

Rollback segment + oracle 8i

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