Persistent Rollback Segment Header Lockouts (8.1.6)

We are encountering the following situation on a 3-tier production system:
Users occasionally inadvertently disconnected from client tier while a long-standing transaction (individual inserts controlled manually) has not yet been committed. (client cannot rejoin the severred session, by the way).
At the point of disconnection, users often appear to be holding a rollback segment header enqueue.
Subsequently, other users are getting locked out by this enqueue as they go for a transaction.
We have 400 active users, and 80 rollback segments (ie. 5 potential transactions per segment). Each RBS is split into an minimum of 16 extents.
My question:
I have been led to believe by Oracle documentation that rollback seg. header locks are only held v. briefly. If this were so, the chances of this situation occurring would be slim. However, we observe this situation occurring daily.
Yes I can up the number of RBS, but is there some other action I could be taking ? - indeed upping the RBS count may have no appreciable impact on this situation at all !

Hi,
Generally "Snapshot too old " error occurs when your rollback segment has not enough space for keeping your undo information. If you still facing that problem even after assigning a big tablespace, means your transaction is taking so much space. You can try to assign some more space in tablespace where you ahve created rollback segment. Have you assigned the tablespace using the same syntax
SET TRANSACTION USE ROLLBACK SEGMENT large_rs1;
For getting more information on this pls go through the following link
http://download-uk.oracle.com/docs/cd/B10501_01/server.920/a96521/undo.htm#9114
Please let me know if you have any other issue.
Thanks

Similar Messages

Rollback segment header contention

Hi,
what does it mean :
rollback segment header contentionWhy does it come ?
How to avoid it ?
Many thanks.

No, automatic undo is 9+ so you have to manage your rollback segments manually. All you need to do is ensure you have enough rollback segments allocated to handle the concurrent tranaction load.
We found we could use a fairly small number of larger rbs segments to handle our OLTP environment.
Remember also that contention is relative to the number of GETs to the rbs header and some waits are to be expected.
HTH -- Mark D Powell --

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>

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.

ORA-1650: unable to extend rollback segment

Hi,
We have 20 RBS's and in our production instance we got very frequent alerts related to ORA-1650: unable to extend rollback segment continuously. When I looked for select STATUS from v$rollstat; I could see most of them are with FULL status. after couple of hours they disappeared and status became online.
How to avoid these type of alerts?
REgards

What version of Oracle?
If you are 9ir2 or later, you should be going to automatic undo management. Though it won't help your 'we cannot add space' restriction. That's not an Oracle problem, that's a corporate issue.
This problem may be caused by poor transaction design with too many processing doing too infrequent commits. That's not an Oracle problem either, that's a corporate/development issue.
So...you don't have an Oracle problem.
You can't stop the 1650s from occurring if you are unwilling to add space or address application issues. However, you can set up an email filter so that any emails containing ORA-01650 in the header or body get automatically sent to the trash.
<sarcasm>
If you can't solve a problem, then just ignore it!
</sarcasm>

Want to decrease size for ROLLBACK Segments

my database is oracle8i. Previous DBA increased rollback size to 18GB. i need space on my unix box.
i want to reduce size of rollback segment and utilized this space for other purpose.
This is my stats
Tablespace Name FILE_NAME SIZE IN MB
ROLLBACK /u01/rbsdata/rbs01.dbf 5000
ROLLBACK /u01/rbsdata/rbs02.dbf 5000
ROLLBACK /u01/rbsdata/rbs03.dbf 6000
There are 12 rollback segments allocated to him
SEGMENT_NAME FILE_NAME SIZE
rbs0 /u01/rbsdata/rbs01.dbf 5000
rbs12 /u01/rbsdata/rbs01.dbf 5000
Now Could any one suggest to reduxe size with best performing and not affected my production database.
Thanks
Chetan

Hi Chetan,
You can adapt the following script as per your needs. It will search for all rollback segments other than 'SYSTEM' and construct the sql order to reduce the size of each rollback segment.
connect user/*******@test
SET SERVEROUTPUT ON size 50000
SET HEAD OFF FEEDBACK OFF VERIFY OFF
SPOOL D:\shrink.sql
BEGIN
     -- RBS to be shrinked
     FOR toto IN (select Segment_Name from DBA_SEGMENTS
where Segment_Type = 'ROLLBACK'
and segment_name not in 'SYSTEM')
     LOOP
          DBMS_OUTPUT.PUT_LINE('alter rollback segment '||toto.Segment_Name||' '||'shrink to 60M;');
     END LOOP;
END;
SPOOL OFF
SET HEAD ON FEEDBACK ON VERIFY ON
spool d:\shrink.log
select to_char(sysdate, 'dd/mm/yyyy hh24:mi:ss') "Shrinked" from dual;
@D:\shrink.sql
spool off
Exit
R.Tirou

Deferred rollback segments

The number of extents is limited by the number of slots in the extent control table in the segment header block.To avoid data loss, you must ensure that that limit is never reached for a deferred rollback segment.
from
http://www.ixora.com.au/tips/creation/bsq.htm
You can make SYSTEM a dictionary managed tablespace with a non-zero PCTINCREASE value and rely on the MINIMUM EXTENT size feature to limit fragmentation. (This feature is not available prior to Oracle8; but nobody should be creating Oracle7 databases anymore.)
how min extent in this case can prevent Fragmentation?
manish

mainly i want to ask is it possible to transfer data dictionary from 1 tablespace to another.
how to find fragmentation in system tablespace.
Manish

Question abt rollback segments

hi all,
I have some doubts on oracle internal architecture. When DML statements are run, the old datablocks are written to rollback segments. But it first happens in SGA and later they will be written to the file by dbwr. Any idea when they will be written? i.e., before commit or after?
Regards
Suresh

This has been running through my head all morning and I did some more tests. For the same demo I get this output:
7624441972          20060419 165120          INSERT     insert into "SYS"."TAB$"("OBJ#","DATAOBJ#","TS#","FILE#","BLOCK#","BOBJ#","TAB#","COLS","CLUCOLS","PCTFREE$","PCTUSED$","INITRANS","MAXTRANS","FLAGS","AUDIT$","ROWCNT","BLKCNT","EMPCNT","AVGSPC","CHNCNT","AVGRLN","AVGSPC_FLB","FLBCNT","ANALYZETIME","SAMPLESIZE","DEGREE","INSTANCES","INTCOLS","KERNELCOLS","PROPERTY","TRIGFLAG","SPARE1","SPARE2","SPARE3","SPARE4","SPARE5","SPARE6") values ('1247473','1247473','5','3','13198',NULL,NULL,'1',NULL,'10','40','1','255','1','--------------------------------',NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,'1','1','536870912','0','736',NULL,NULL,NULL,NULL,TO_DATE('19/04/06', 'DD/MM/RR'));
7624441972          20060419 165120          INSERT     insert into "SYS"."COL$"("OBJ#","COL#","SEGCOL#","SEGCOLLENGTH","OFFSET","NAME","TYPE#","LENGTH","FIXEDSTORAGE","PRECISION#","SCALE","NULL$","DEFLENGTH","SPARE6","INTCOL#","PROPERTY","CHARSETID","CHARSETFORM","SPARE1","SPARE2","SPARE3") values ('1247473','1','1','22','0','A','2','22','0',NULL,NULL,'0',NULL,NULL,'1','0','0','0','0','0','0');
7624441972          20060419 165120          INTERNAL
7624441972          20060419 165120          INTERNAL
7624441972          20060419 165120          INTERNAL
7624441972          20060419 165120          DDL     create table T
a number
7624441973          20060419 165120          UPDATE     update "SYS"."SEG$" set "TYPE#" = '5', "BLOCKS" = '64', "EXTENTS" = '1', "INIEXTS" = '64', "MINEXTS" = '1', "MAXEXTS" = '2147483645', "EXTSIZE" = '64', "EXTPCT" = '0', "USER#" = '44', "LISTS" = '0', "GROUPS" = '0', "CACHEHINT" = '0', "HWMINCR" = '1247473', "SPARE1" = '131329' where "TS#" = '5' and "FILE#" = '3' and "BLOCK#" = '13198' and "TYPE#" = '3' and "BLOCKS" = '64' and "EXTENTS" = '1' and "INIEXTS" = '64' and "MINEXTS" = '1' and "MAXEXTS" = '2147483645' and "EXTSIZE" = '64' and "EXTPCT" = '0' and "USER#" = '44' and "LISTS" = '0' and "GROUPS" = '0' and "BITMAPRANGES" = '0' and "CACHEHINT" = '0' and "SCANHINT" = '0' and "HWMINCR" = '1247473' and "SPARE1" = '131329' and "SPARE2" IS NULL and ROWID = 'AAAAAIAABAAADxHAAY';
7624441975     7624441975     20060419 165120     20060419 165120     COMMIT     commit;
7624441977          20060419 165127          START     set transaction read write;
7624441977          20060419 165127          INSERT     insert into "YJAM"."T"("A") values ('1');
7624441979          20060419 165133          INSERT     insert into "YJAM"."T"("A") values ('2');
7624442016     7624442016     20060419 165322     20060419 165322     COMMIT     commit;
7624442021          20060419 165334          START     set transaction read write;
7624442021          20060419 165334          INSERT     insert into "YJAM"."T"("A") values ('3');
7624442025     7624442025     20060419 165341     20060419 165341     COMMIT     commit;     (I don't know if the formatting will be OK since it's a SQL Developer copy/pase and I don't have a clear formatted output there anyway)
Field 2 is the "CSCN" which I think is the Commit SCN, since it appears only on commit.
So now, I can only agree with you Mark, that the transaction SCN is actually defined when the transaction ends. But I still think that for transaction read concistency, the SCN used through the ransaction is the one of the transaction start (START - set transaction read write).
Regards,
Yoann.

Creating more rollback segments

Hi,
in a performence report we have :
Contention for undo header = 2.35%
Contention for undo block = 15.34%
If the percentage for an area is more than 1% or 2%, consider
creating more rollback segments.
Does it mean that we should add a file to rollback tablespace ? Is it the only action ? how to create more rollback segments ?
what should we do ?
regards

Try setting UNDO_MANAGEMENT=AUTOIf big1362000 (presumably Big1 to his friends) is still using rollback segments then they shouldn't switch to automatically managed UNDO without a little thought and some impact analysis. However, given the version of the database they're on I think moving to an UNDO tablespace is the better plan in the long run.
Big1362000
Does it mean that we should add a file to rollback tablespace ? No. It means create more rollback segments. You may want/need to add another datafile to the tablesapce used by the rollback segments or even create a new tablespace for the new rollback segments (depending on what your policy is). However, your really ought to think about progressing to Automated Undo Management (it's the wave of the future).
Cheers, APC

Maintenance on Rollback segments

Hello experts,
i need some pieces of advice.
1. Is there some maintenance that should be done regularly on my
Rollback segments?
2. Any guidelines for the creation of rollback segments?
3. how will i know if there is a contention on rollback segments?
thanks for your replies
regards
yogeeraj

Pretty large subject -- there are entire chapters written on
RBseg useage in various Oracle manuals.
In general (knowing you will take it upon yourself to start
reading up on RBsegs in the manuals):
1) I always create the largest RBsegs possible given a thorough
knowledge of the range of typical transactions. That way I spend
less time managing large queries from bone-head users who should
know better <grin>. On 8x systems use the ALTER ROLLBACK
SEGMENT... SHRINK on a periodic basis to release space to other
RBsegs.
FYI: RBsegs are going away in 9i, check out the new 9i UNDO
TBspace.
2) don't mix RBsegs with data and index space. Always put RBsegs
in their own tablespace to avoid TX contention. I always create
RBsegs with auto allocate TBS and datafiles.
3) way too much to say on the subject of RBseg contention but...
try to attain zero wait time on RBsegs. KNOW when your users are
running WHAT jobs and steer them towards run-times that favour
the entire DB resources.
RP.
Hello experts,
i need some pieces of advice.
1. Is there some maintenance that should be done regularly on my
Rollback segments?
2. Any guidelines for the creation of rollback segments?
3. how will i know if there is a contention on rollback segments?
>
>
thanks for your replies
regards
yogeeraj

Creating rollback segments

I would like to know how to create the perfect rollback segments.
I currently have a database that is up and running, but I feel that the rollback segments, are not running at there best.
I know that the minextents should be set to 20 extents, inital and next are to be the same, but I don't know what the best optimal figure should be.
Looking at the view $waitstat, "undo header" is at a non-zero figure, so this has prompted me to re-configure the rollback segments. Currently the highest HWMSIZE is 45m, and the highest AVEACTIVE is 3m.
Can anyone help?

Hi
ORA-01552: cannot use system rollback segment for non-system tablespace 'string'
Cause: An attempt was made to use the system rollback segment for operations involving non-system tablespace. If this is a clone database then this will happen when attempting any data modification outside of the system tablespace. Only the system rollback segment can be online in a clone database.
Action: Create one or more private/public segment(s), shut down and restart. May need to modify the initialization parameter ROLLBACK_SEGMENTS to acquire private rollback segment. If this is a clone database being used for tablespace point in time recovery then this operation is not allowed.
Hope this helps
-Aditi

Rollback segment Error coming for 8 lacks Record while creating MV

Hi All,
i am creating a materialized View and it gives us 8 lacks record but when we creates in production its fails due to rollback segment does not have enough space to handle it and it did not create the MV.
can anyone help me out to resolve this issue for the below query while creating MV.
SELECT DISTINCT NVL
((ROUND ((jt_date_completed - jt_date_requested) * 24, 2)
0
) AS actual_hrs_to_complete,
NVL ((ROUND ((jt_date_responded - jt_date_requested) * 24, 2)
0
) AS actual_hrs_to_respond,
peo1.peo_name AS agent_name,
peo1.peo_user_name AS asagent_soe_id,
le.lglent_desc AS ap_system,
' ' AS assign_work_request_comment,
DECODE (jt.jt_bill_id,
138802, 'CLIENT BILLABLE',
138803, 'CONTRACTED',
138804, 'INTERNAL BILLABLE',
NULL, ' '
) AS billable,
bl.bldg_name_cc AS building, bl.bldg_id_ls AS building_id,
DECODE (bl.bldg_active_cc,
'Y', 'ACTIVE',
'INACTIVE'
) AS building_status,
DECODE (jt.jt_wrk_cause_id,
141521, 'STANDARD WEAR AND TEAR',
141522, 'NEGLIGENCE',
141523, 'ACCIDENTAL',
141524, 'MECHANICAL MALFUNCTION',
141525, 'OVERSIGHT',
141526, 'VANDAL',
141527, 'STANDARD',
141528, 'PROJECT WORK',
6058229, 'TEST',
NULL, ' '
) AS cause_type,
' ' AS comments, peo3.peo_name AS completed_by,
jt.jt_requestor_email AS contact_email,
jt.jt_requestor_name_first
|| ' '
|| jt.jt_requestor_name_last AS contact_name,
jt.jt_requestor_phone AS contact_phone,
cc.cstctrcd_apcode AS corp_code,
cc.cstctrcd_code AS cost_center,
jt.jt_date_closed AS date_closed,
jt.jt_date_completed AS date_completed,
jt.jt_date_requested AS date_requested,
jt.jt_date_responded AS date_responded,
jt.jt_date_response_ecd AS date_response_ecd,
jt.jt_date_scheduled AS date_scheduled,
DECODE (jt.jt_def_id,
139949, 'WTG VENDOR RESPONSE',
139950, 'WAITING ON PARTS',
139951, 'LABOR AVAILABILITY',
139952, 'DEFERRED- HI PRI WORK',
139953, 'WTG APPROVAL',
139954, 'FUNDING REQUIRED',
139955, 'ACCESS DENIED',
139956, 'WTG MATERIAL',
NULL, ' '
) AS deferral_reason,
jt.jt_description AS description,
jt.jt_date_resched_ecd AS ecd,
fmg.facility_manager AS facility_manager,
fl.floors_text AS FLOOR, gl.genled_desc AS general_ledger,
' ' AS kiosk_date_requested, ' ' AS kiosk_dispatch_confirmed,
' ' AS kiosk_dispatched,
eqp.equip_customer_code AS linked_equipment_alias,
eqp.equip_id AS linked_equipment_id,
eqp.equip_text AS linked_equipment_name,
DECODE (jt_originator_type_id,
1000, 'PROJECT MOVE REQUEST',
138834, 'CUSTOMER INITIATED CORRECTION',
138835, 'CUSTOMER INITIATED REQUEST',
138836, 'CORRECTIVE MAINTENANCE',
138837, 'CONFERENCE ROOM BOOKING',
138838, 'PROJECT INITIATED REQUEST',
138839, 'PLANNED PREVENTIVE MAINTENANCE',
138840, 'SELF INITATED REQUEST',
NULL, ' '
) AS originator_type,
' ' AS payment_terms, priority_text AS priority_code,
swoty.sworktype_text AS problem_type,
prop.property_name_cc AS property,
jt.jt_cost_quote_total AS quote_total,
par.levels_name AS region,
DECODE (jt.jt_repdef_id,
141534, 'ADJUSTED SETTING',
141535, 'TRAINING FOR END',
141536, 'NEW REQUEST',
141537, 'NO REPAIR REQUIR',
141538, 'REPLACED PARTS',
141539, 'REPLACE EQUIPMEN',
1000699, 'NEW REQUEST',
NULL, ' '
) AS repair_definitions,
jt.jt_repairdesc AS repair_description,
jt.jt_requestor AS requestor, ' ' AS requestor_cost_center,
jt.jt_requestor_email AS requestor_email,
jt.jt_requestor_name_first AS requestor_name,
jt.jt_requestor_phone AS requestor_phone,
' ' AS response_time, rm.room_name_cc AS room,
p1.peo_provider_code1 AS service_provider,
p1.peo_address_1 AS service_provider_address,
peocity.city_text service_provider_city,
p1.peo_provider_code1 AS service_provider_code,
peocity.city_country_name AS service_provider_country,
peocur.currency_text AS service_provider_currency,
p1.peo_name AS service_provider_description,
p1.peo_dispatch_method AS serv_prov_dispatc_hmethod,
p1.peo_rate_double AS serv_prov_double_time_rate,
p1.peo_email AS service_provider_email,
p1.peo_emergency_phone AS serv_prov_emergency_phone,
p1.peo_fax AS service_provider_fax_number,
p1.peo_home_phone AS service_provider_home_phone,
p1.peo_rate_hourly AS service_provider_hourly_rate,
p1.peo_title AS service_provider_job_title,
p1.peo_method_id AS service_provider_method,
p1.peo_cell_phone AS service_provider_mobile_phone,
p1.peo_pager AS service_provider_pager,
p1.peo_rate_differential AS service_provider_rates,
p1.peo_rate_differential AS ser_prov_shift_differential,
peocity.city_state_prov_text AS serv_prov_state_province,
DECODE (p1.peo_active,
'Y', 'ACTIVE',
'INACTIVE'
) AS service_provider_status,
p1.peo_url AS serv_prov_web_site_address,
p1.peo_phone AS service_provider_work_phone,
p1.peo_postal_code AS serv_prov_zip_postal_code, ' ' AS shift,
' ' AS skill,
DECODE (jt.jt_bigstatus_id,
138813, 'NEW',
138814, 'PENDING',
138815, 'OPEN',
138816, 'COMPLETED',
138817, 'CLOSED',
138818, 'CANCELLED',
NULL, ' '
) AS status,
lev.levels_name AS subregion, ' ' AS trade,
p1.peo_ls_interface_code1 AS vendor_id,
p1.peo_fax AS vendor_purchasing_fax,
p1.peo_vendor_site_code AS vendor_sitecode,
jt.jt_id AS vendor_ticket, p1.peo_name AS vendor_companyname,
jt.jt_requestor_vip AS vip, wo.wo_id AS work_order_no,
jt.jt_id AS work_request,
jt.jt_class_id AS work_request_class,
woty.worktype_text AS work_type, ' ' AS wr_cost,
jt.jt_description AS wr_description,
' ' AS wr_dispatch_method,
DECODE (jt.jt_bigstatus_id,
138813, 'NEW',
138814, 'PENDING',
138815, 'OPEN',
138816, 'COMPLETED',
138817, 'CLOSED',
138818, 'CANCELLED',
NULL, ' '
) AS wr_status,
ctry.country_name AS country
FROM citi.jobticket jt,
citi.property prop,
citi.bldg bl,
citi.bldg_levels bldglvl,
citi.LEVELS lev,
citi.LEVELS par,
(SELECT crstools.stragg (peo_name) facility_manager,
bldgcon_bldg_id
FROM citi.bldg_contacts, citi.people
WHERE bldgcon_peo_id = peo_id
AND bldgcon_contype_id IN (40181, 10142)
GROUP BY bldgcon_bldg_id) fmg,
citi.floors fl,
citi.room rm,
citi.general_ledger gl,
citi.legal_entity le,
citi.cost_center_codes cc,
citi.equipment eqp,
citi.worktype woty,
citi.subworktype swoty,
citi.work_order wo,
citi.jt_workers jtwo,
citi.priority,
citi.country ctry,
citi.people p1,
citi.people peo3,
citi.people peo1,
citi.city peocity,
citi.currency peocur
WHERE jt.jt_bldg_id = bl.bldg_id
AND bl.bldg_id = bldglvl.bldg_levels_bldg_id
AND bldglvl.bldg_levels_levels_id = lev.levels_id
AND lev.levels_parent = par.levels_id(+)
AND prop.property_id = bl.bldg_property_id
AND bl.bldg_active_ls <> 'N'
AND jt.jt_floors_id = fl.floors_id(+)
AND jt.jt_room_id = rm.room_id(+)
AND jt.jt_bldg_id = fmg.bldgcon_bldg_id(+)
AND jt.jt_genled_id = gl.genled_id(+)
AND gl.genled_lglent_id = le.lglent_id(+)
AND jt.jt_cstctrcd_id = cc.cstctrcd_id(+)
AND jt.jt_equip_id = eqp.equip_id(+)
AND jt.jt_id = jtwo.jtw_jt_id(+)
AND jt.jt_worktype_id = woty.worktype_id(+)
AND jt.jt_sworktype_id = swoty.sworktype_id(+)
AND jt.jt_wo_id = wo.wo_id
AND jt.jt_priority_id = priority_id(+)
AND jt.jt_date_requested >= ADD_MONTHS (SYSDATE, -12)
AND bl.bldg_country_id = ctry.country_id
AND jtwo.jtw_peo_id = p1.peo_id(+)
AND p1.peo_city_id = peocity.city_id(+)
AND jt.jt_completed_by_peo_id = peo3.peo_id(+)
AND p1.peo_rate_currency_id = peocur.currency_id(+)
AND jt.jt_agent_peo_id = peo1.peo_id(+);
Regards
shyam~

Hi,
Its ora-1555? IS your undo_retention sufficient?
Since you are developer the only option you have is to tune the query?
Am curious to know like I create materialized view so that I do not have to run complex query on the master database / or to prevent the access to master database more than once to get the same data?
Like to know which is your case because your query seem to be too complex to be the case for former. Do you think this materialized view would be used frequently in your application?
Regards
Anurag Tibrewal.

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.

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

Persistent Rollback Segment Header Lockouts (8.1.6)

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