Rollback segments & UNDO (8i to 10g migration)

Hello all,
I need to migrate a database from 8.1.0.7 (server a) to 10.1.0.2 (server b) on HPUX and I am going through pre-tasks for IMP.
On 8i:
Tablespace name: RBS
4 Rollback segments on RBS tablespace
1 System Rollback segment, on SYSTEM tablespace
On 10g:
Pre-created UNDO01 tablespace
4 Undo on UNDO01 tablespace
1 Undo on SYSTEM tablespace
My question is, can i run IMP full=y as is?
Or should I pre-create the Rollback Tablespace & rollback segments on 10g also?
If this is the case, what should my init.ora parameter show?
#rollback segments
rollback_segments = (acbr01,acdbr02,acdbr03,acdbr04)
#undo
undo_segments
undo_management = auto
undo_tablespace = undo01
Thanks!

Hi..
You can use IMP full=y, there is no need to create rollback segments in 10g. In init file mention you need to mention
#undo
undo_segments
undo_management = auto
undo_tablespace = undo01
The import utility will use UNDO tablespace, so keep monitoring it.
Anand

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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
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What is the difference between Undo segment & Rollback segment?Is it a standard practice of creating roll back segments for each tablespace?
Regards,
Cherry

What is the difference between Undo segment & Rollback segment?
Undo Mode
Undo mode provides a more flexible way to migrate from manual undo management to automatic undo management. A database system can run in either manual undo management mode or automatic undo management mode. In manual undo management mode, undo space is managed through rollback segments. In automatic undo management mode, undo space is managed in undo tablespaces. To use automatic undo management mode, the database administrator needs only to create an undo tablespace for each instance and set the UNDO_MANAGEMENT initialization parameter to AUTO. You are strongly encouraged to run in automatic undo management mode.
Is it a standard practice of creating roll back segments for each tablespace?See above and http://download-uk.oracle.com/docs/cd/B19306_01/server.102/b14220/logical.htm#sthref449

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Hi,
What determines the max rollback segments in 10g? I know that the max rollback segments is min(ceil(transactions/transactions_per_rollback_segments),max_rollback_segments) in 9i.
Thanks

In Oracle 10g you should use automatic undo management so that you don't need to care about number of rollback segments but let Oracle manage automatically the number of undo segments.

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dear all.
db: oracle 10.2.0.1
os: rhel as version 5 64 bits.
This is a testing database. And my database is online and open. But i can free the external usb disk that contains my ols undotbs.
I want to drop old undo tablespace but this is not possible.
1.- In order to open my database i had my datafile( '/mnt/hdext/back_plelds/undotbs02.dbf') offline drop, and then i can to open my database.
2.- When i try to delete my old undo tablespace im getting this error:
SQL> drop tablespace undotbs1 including contents and datafiles;
drop tablespace undotbs1 including contents and datafiles
ERROR at line 1:
ORA-01548: active rollback segment '_SYSSMU1$' found, terminate dropping
tablespace
3.- My default undo_tablespace is another that i was created before step 1.
SQL> sho parameter undo_ta
NAME TYPE VALUE
undo_tablespace string UNDOTMP
SQL>
Well i search in metalink ORA-01548 code error and in 18947.1 doc whows me that the solution is:
Action: Shut down instances that use the active rollback segments in the
tablespace and then drop the tablespace.
4.- I try to shutdown but im getting:
SQL> shutdown immediate;
ORA-00376: file 10 cannot be read at this time
ORA-01110: data file 10: '/mnt/hdext/back_plelds/undotbs02.dbf'
SQL>
This /mnt/hdext is an external USB disk and i have all permissions. I exported tables without any problem and i can read all files.
i search un metalink again ora codes (ORA-00376 ORA-01110) and the doc id: 427801.1 shows in the solution:
Drop the old undo tablespace instead of making it offline.
but when i try to drop the tablespace it shows the error describe in the step 2.
Facts:
- my tablespace UNDOTBS1 is ONLINE. I put in offline and this is not the solution.
- This is the status of my rollback segments:
SQL> select segment_name, status from dba_rollback_segs where
2 tablespace_name='UNDOTBS1';
SEGMENT_NAME STATUS
_SYSSMU1$                      NEEDS RECOVERY
_SYSSMU2$                      NEEDS RECOVERY
_SYSSMU3$                      NEEDS RECOVERY
_SYSSMU4$                      NEEDS RECOVERY
_SYSSMU5$                      NEEDS RECOVERY
_SYSSMU6$                      NEEDS RECOVERY
_SYSSMU7$                      NEEDS RECOVERY
_SYSSMU8$                      NEEDS RECOVERY
_SYSSMU9$                      NEEDS RECOVERY
_SYSSMU10$                     NEEDS RECOVERY
_SYSSMU11$                     OFFLINE
SEGMENT_NAME STATUS
_SYSSMU12$                     OFFLINE
12 rows selected.
SQL>
- I have the note (Unable to drop und tablespace In this article describe the problem but this is not the same. The difference is that i cannot drop the rollback segment that describe in step 2.
SQL> drop rollback segment "_SYSSMU1$";
drop rollback segment "_SYSSMU1$"
ERROR at line 1:
ORA-30025: DROP segment '_SYSSMU1$' (in undo tablespace) not allowed
in metalink the doc id: 173696.1 shows the solution:
Action:     Check the undo segment name and reissue statement if necessary.
i cannot drop the rollback_segment
What can i do ???
thanks a lot.

in step 4 did you try with shutdown abort?
If its still does not work then create another new table space with new file and then swtich to that tablespace http://download.oracle.com/docs/cd/B19306_01/server.102/b14231/undo.htm#sthref1504Khurram

Illegal rollback Segment operation in Automatic Undo mode

Hi,
I use oracle database 9.2.0.1 and I try to install SCM repository but when I run ckcreate I saw an error message in
the log file that Illegal rollback Segment operation in Automatic Undo mode because oracle 9.2 use automatic undo mode .So how can i install the repository.
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Replacing explicit Rollback Segments by UNDO segement

Hi,
My DBA wants to turn off the explicit rollback segments currently being used and replace them by UNDO segment. I have explicit mention of these rollback segments in my C++ and Pro*C codes. What changes am I supposed to make in order to implement the UNDO segements. Do I need to remove the function or only commenting the rollback segment reference line will suffice. Please see the sample code below:
void DeleteDBI::SetTransaction()
struct sqlca sqlca;
EXEC SQL BEGIN DECLARE SECTION;
// Thread context:
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EXEC SQL END DECLARE SECTION;
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EXEC SQL WHENEVER SQLERROR DO SqlError(sqlca, "DeleteDBI::SetTransaction");
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It looks like you can comment the entire procedure.
However it is not a good practice to control the Rollback segment from code.
Check with ur DBA for better options in the future.

Oracle9i How to convert from undo tables to rollback segments

Hi,
Anyone try before converting from UNDO management to using rollback segment....What are the procedures for the conversion...
Thank You...

Hi,
Follow these steps to convert from Auto UNDO to Rollback Segs....
1. With the database opened, create a rollback tablespace and then create some rollback segments and bring them online like this
CREATE ROLLBACK SEGMENT RBS1 TABLESPACE RBS;
ALTER ROLLBACK SEGMENT RBS1 ONLINE;
2. Then edit the PFILE and modify these parameters
Add: ROLLBACK_SEGMENTS=(RBS1,RBS2,RBS3....)
Comment: UNDO_MANAGEMENT=AUTO and UNDO_TABLESPACE=UNDOTBS or whatever name you have for your UNDO tablespace.
3. Shutdown the database gracefully(normal).
4. Startup pfile=<Pfile path>
5. Sync these new parameter changes to the SPFILE by recreating the SPFILE.
6. Take a full level 0 backup of your database as the structure has changed.
The next time you start the database, it will use the SPFILE which is same as the PFILE.
Regards.

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

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First, I created a database for a vendor with an Undo Tablespace UNDOTBS. Then the vendor requested me to create rollback segments instead. So I created a new tablespace RBSTBS just to hold these segments. When I tried to create the rollback segment using the newly created tablespace RBSTBS, it complained that I am not allowed to use non-system tablespaces.
So instead, I used the Undo tablespace UNDOTBS to hold the rollback segment. It worked.
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Another thing, the vendor wanted me to create rollback segments of 200MB each. Where do I set this while creating the rollback segment? Is this the INITIAL, NEXT, or OPTIMAL size?
I know that Oracle recommends using UNDO rather than rollback segments. Is there any advantage in using traditional rollback segments?
Thanks for any help!

Advantage with rollback segment is you can force your transaction to use any specific rollback segment, where as with undo you don't have any control. Oracle does it for us.
Thanks and Regards,
Satheesh Babu.S
Bangalore.

Tablespace, Rollback segments and Undo tablespace

hi,
we are frequently getting an error on tablespaces, rollback segments and undo tabelspaces during the ETL load. This was really distrubing us to go further, is there any best practice how to avoid the tablespace errors or any precautions to be taken, we are very new to this ETL loads, pls advice
Kishan

Hello Kishan
Yes. Make tablespaces bigger. However, the proper way to do it is optimizing your queries. If you don't have experience with Oracle DB, consult your DBA.
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Mate

Difference Between Rollback Segments and UNDO Tablespace

Hi guys,
Can you tell difference between Rollabck segments and UNDO Tablespaces.
I think that rollback Segemnts and UNDO tablespaces are similar both are used for storing before imags of data, which is going to be modified.
but my question still both the rollback abck segments and UNDO tablespaces exists.
why and what is the reason of both existing and at what time, we can use..them at which scenarios's
Regards,
Pavan Kumar N

Undo segments in undo tablespaces, introduced in 9i, are the successor of rollback segments.
They are automatically managed by Oracle.
Rollback segments exist for reasons of backwards compatibility.
That said, you should switch to undo segments and stop using rollback segments.
Other than that: could you please avoid rehearsing the complete documentation in this forum?
Sybrand Bakker
Senior Oracle DBA

R0 Rollback Segment in Import of 10gR2 into 11gR2 Database

I have a new install of Oracle Database Server Enterprise Edition 11.2.0.3.6 on AIX 7.1.
I used the DBCA to create two databases and used export datapump and import datapump to upgrade two 10gR2 database to 11gR2.
One of the import logs includes the following messages:
Processing object type DATABASE_EXPORT/ROLLBACK_SEGMENT
ORA-39083: Object type ROLLBACK_SEGMENT failed to create with error:
ORA-02221: invalid MAXEXTENTS storage option value
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I can copy and modify the CREATE ROLLBACK statement and lower the value assigned to MAXEXTENTS, or use MAXEXTENTS UNLIMITED, then run the command in the target database.
In light of the fact that the DBCA did not create R0 in my two 11gR2 databases, I want to know if I still need to create R0 in the one that showed the error in the import log. Has anyone else noticed the disappearance of R0?
Here are the rollback segments that exist in the 11gR2 database at this time:
SQL> Select SEGMENT_NAME, OWNER, TABLESPACE_NAME, INITIAL_EXTENT, NEXT_EXTENT, MIN_EXTENTS, MAX_EXTENTS, PCT_INCREASE, STATUS
from SYS.DBA_ROLLBACK_SEGS;
SEGMENT_NAME OWNER TABLESPACE_NAME INITIAL_EXTENT NEXT_EXTENT MIN_EXTENTS MAX_EXTENTS PCT_INCREASE STATUS
SYSTEM SYS SYSTEM 114688 57344 1 32765 ONLINE
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_SYSSMU2_3033359625$ PUBLIC UNDOTBS1 131072 65536 2 32765 ONLINE
_SYSSMU3_2670780772$ PUBLIC UNDOTBS1 131072 65536 2 32765 ONLINE
_SYSSMU4_286801445$ PUBLIC UNDOTBS1 131072 65536 2 32765 ONLINE
_SYSSMU5_1738828719$ PUBLIC UNDOTBS1 131072 65536 2 32765 ONLINE
_SYSSMU6_3548494004$ PUBLIC UNDOTBS1 131072 65536 2 32765 ONLINE
_SYSSMU7_700714424$ PUBLIC UNDOTBS1 131072 65536 2 32765 ONLINE
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_SYSSMU9_2087597455$ PUBLIC UNDOTBS1 131072 65536 2 32765 ONLINE
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11 rows selected.
Thanks,
Bill

Srini,
Both the 10gR2 and 11gR2 versions of the database are using automatic undo management.
Connected to:
Oracle Database 10g Enterprise Edition Release 10.2.0.2.0 - 64bit Production
With the Partitioning, OLAP and Data Mining options
SQL> show parameter undo
NAME TYPE VALUE
_undo_autotune boolean TRUE
undo_management string AUTO
undo_retention integer 14400
undo_tablespace string UNDOTBS1
SQL>
Connected to:
Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - 64bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options
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NAME TYPE VALUE
undo_management string AUTO
undo_retention integer 14400
undo_tablespace string UNDOTBS1
SQL>
Do you know anything about Oracle no longer automatically creating R0 in 11gR2?
Thanks,
Bill

Rollback segment number not shown with name " not shown " too small

Hi,
we have a table TABLE1 with a BLOB field FIELD1 on a Oracle 10g database. Today we found out that there is one record in that table that make problems. if we try to read the BLOB data from that record, Oracle shows the error:
ORA-01555: snapshot too old: rollback segment number with name "" too small
The strange thing about it, that the message shows neither the segment number nor the segment's name. Like it has lost the reference to it.
Could you help please.
Notes:
The TABLE1 and the BLOB data are really not big.
The UNDO tablespace is 2Gb big and just 1% used.
Thank you very much
Igor

Out-of-row LOB undo is maintained in the LOB segment. So the UNDO tablespace and undo retention is not associated with most LOB ORA-1555 issues. Instead the LOB column is created using either PCT_VERSION or RETENTION to manage how much space within blocks or time transpires before the LOB undo is overwritten. In environments with high updates, deletes on rows including LOBs, the chances of ORA-1555 on LOB undo is very high.
Source:http://blogs.oracle.com/db/entry/troubleshooting_ora_1555
In the above link you will get plenty of good metalink notes to understand and solve the issue.
There is no undo segment name in the error message means this error has no relation with undo tablespace/parameter/segment. This might mean that your LOB table is corrupted. Can you drop and recreate/re-populate this table and try again ?
Srini Chavali @ Another "snapshot too old: rollback segment number with name "" too small"
Regards
Girish Sharma

ORA01555"snapshot too old:rollback segment num %s with name "%s" to small

Hi All
i have and 11gR1(11.1.0.6) DB source instance in wich i have i a partitioned table of 1TB size.
I want to IMPDP this table using NETWORK_LINK in a 11gR2(11.2.0.3) destination RAC instance.
when a try to import a get the following error message
ORA 01555 "snapshot too old: rollback segment number %s with name \"%s\" too small"
UNDO_RETENTION=130000
UNDOTBS1=300GB
UNDOTBS2=220GB
i have searche dhte metalink docs but did not find any solution.
is there any hint or document to follow?
thanks in advance
Soni

Hi,
Stopping the loading may work - it there is no other activity going on then you should be OK.
If you want to guarantee the undo doesn't get overwritten for the length of the export you can run switch on guarantee undo retention for the undo tablespace - by default it is just a target not a guarantee - see this link for more details:
http://www.oracle-base.com/articles/10g/space-object-transaction-management-10g.php
Regards,
Harry

Rollback segments & UNDO (8i to 10g migration)

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