Segment shrinking and UNDO tablespace

When i issued
alter table <table_name> shrink space cascade;
I got the error 'Unable to extend UNDO ...by 8' . Does Segment shrinking consume space from UNDO tablespace?
Message was edited by:
for_good_reason

As Jonathan said, shrinking segment generates redo and undo data.
But, this phoenomenon of undo shortage is not normal case.
Shrinking segment might invole continous DML(deleting and re-inserting),
but it's transaction seems to be committed internally at regular intervals.
For this reason, shrinking operation should not hold undo area that long.
But have no knowledge on exact behavior of shrink operation.
Someone else will shed a light.
How big your table and indexes?
Some cases are reorted that shrinkage on big segment generates really large amount of undo data.
This might be related with your problem. But not sure.
Visit metalink note# 3888229.

Similar Messages

Differance between Rollback Segements and Undo Tablespace/segments

Hi everyone.
I have some confusion that how Rollback Segements and Undo Tablespace/segments and different? Functionally they seem to be the same but why then Oracle recommends not using Rollback segments?...please explain. Kindly post any links useful in this regard.
Thanks,
Mukesh

1.when does the changed data written to the undo tablespace?It never gets moved to the undo tablespace.
The ORIGINAL data gets moved to the rollback/undo. Oracle assumes that most of the time the transaction is going to commit, so the change is made to the real block (in memory). At that time, enough information to roll back that change is written into the rollback segment.
2.which process writes the changed data to the undo tbs?The server process. The one to which the user connects. The one the user gets by contascting the listener.
3.What are the identifiactions which is used to undo the changes made(like SCN) ? plz...AFAIK, Transaction Id is the only thing used. SCN, a redo log construct, may be used to recreate the transaction ID in the rollback.

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

Cannot shrink the undo tablespace

Hello!
I have run a very long procedure, which generated 15GB undo information. Now I can see in the enterprise manager, that the undo tablespace is empty again. I tried to resize the datafile, but I receive "*ORA-03297*: file contains used data beyond requested RESIZE value". How can I shrink the tablespace without dropping and recreating it?
I tried also
purge recyclebin;
I still get ORA-03297 if I try to resize the datafile.
I wanted to try something like
ALTER TABLE xxxxx UNALLOCATE UNUSED;
or
ALTER TABLE xxxxx SHRINK SPACE;
but are there any tables that save the undo information?
Regards.

Hi
well, my transaction is ready! The undo tablespace has not more that 10M of information, the other 15G are free!
Thanks for the answers, it seems that i still have recreate it ...
Well, another quertion:
Is it possible, that I just have to wait longer before I resize the undo data file? I have just succeeded in resizing the data file to 7 GB. I really wish I could shrink it to 100M or so, but still - from 15G to 7G is a lot better! 2 hours ago this action was not possible. Is it some automatic management, that needs to time-out before I can shrink the undo tablespace?
Edited by: user10962462 on Apr 8, 2009 2:39 AM

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.
Hope this helps
Mate

Unable to shrink/resize undo tablespace

Hi Experts,
I have Oracle 10.2.0.4 database running on RHEL 4.7 in production environment, my undo tablespace has grown upto 32 GB, database is rebooted, still the tablespace is full.
I want to shrink, resize the undo tablespace, please help me
Few details are as below
show parameter undo_retention
NAME TYPE VALUE
undo_retention integer 10
Please help
Thanks

This post is repeatedly executed by mistake, thread with same name is posted 2 minutes before this
Edited by: user1687821 on Jul 9, 2010 9:29 AM

About snapshot too old and undo tablespace

Hello,
version: 11.1.0.7
environment:
Database A contain some views from several tables located into database B.
When I query the views that join several tables located in a remote database B using a dblink the query intermittently notice me, the following errors:
ORA-12801: error signaled in parallel query server
ORA-01555: snapshot too old: rollback segment number too small
Some times after the I re-execute the query it run without any problems but it is bad because the Developers can not accurately test their app.
The undo tablespace have the following configuration:
guaranteed retention
unlimited
undo_retention is about 7200.
Also the undo tablespace are just using a 4% of total so I think the system should has honor to the old images from my distributed query.
Thank you in advance for your suggestion.

user12100209 wrote:
Hello,
version: 11.1.0.7
environment:
Database A contain some views from several tables located into database B.
When I query the views that join several tables located in a remote database B using a dblink the query intermittently notice me, the following errors:
ORA-12801: error signaled in parallel query server
ORA-01555: snapshot too old: rollback segment number too small
Some times after the I re-execute the query it run without any problems but it is bad because the Developers can not accurately test their app.
The undo tablespace have the following configuration:
guaranteed retention
unlimited
undo_retention is about 7200.
Also the undo tablespace are just using a 4% of total so I think the system should has honor to the old images from my distributed query.
Thank you in advance for your suggestion.session reporting ORA-01555 is victim.
some session is doing DML against same table as victim session & doing COMMIT (likely inside LOOP)

Temp and undo tablespace

Once we created a new temporary or undo tablespace we can make then the default one.My question is regardless of how many undotablespaces or temporary tablespaces the database has the only one used are the assigned as the defualt.Is this right?
Thanks in advnance

Hi, if you user AUM (automatic undo )you can have only one UNDO TS per instance, set by UNDO_TABLESPACE parameters.
For TEMPORARY tablespace you can have several, each user is assigne an TEMPORAY TS by create user....TEMPORARY TABLESPACE name or modified by alter user.

Shrinking undo Tablespace

Shrinking undo Tablespace
What is the preferred why to shrink the UNDO Tablespace ?
1.     To create new UNDO TBS , order the DB to work whit it , and drop the oldest.
2.     To shrink (resize) the exists one .

Sagi wrote:
Shrinking undo Tablespace
What is the preferred why to shrink the UNDO Tablespace ?
1.     To create new UNDO TBS , order the DB to work whit it , and drop the oldest.
2.     To shrink (resize) the exists one .The first one would be a better approach as there may be users who are still using the old tablespace. So for all of them, you would see a Pending Offline status. Once all teh segments release the old information stored in them, you can remove the tablespace. By trying to shrink the tablespace, you actually would be increasing the chances to get the 1555 error and also, this won't be happening as already there is a used space in teh datafile.
HTH
Aman....

Cannot drop old undo tablespace. Cause: active rollback segment

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

Managing Undo tablespace & roll back segments

Hi,
I have oracle 9.1 version and have created 5g undo tablespace apart from 20m rbs tablespace for 15 rollback segments. But it is seen that whenever i give UNDO_MANAGEMENT=AUTO then rollback segments are created using undo tablespace and not allowing rollback segment in rbs tablespace ONLINE. In the reverse happens whenever I give UNDO_MANAGEMENT=MANUAL , the rollback segments in the rbs tablespace gets focus and roll back segments in the Undo tablespace goes offline. Is there anything that I can do so that both undo tablespace and redo segments in the rbs tablespace gets working together so as to minimize the undo contention. Moreover, any query given takes long time when select query given with || in the subquery.
Please suggest the tuning need to do?

brain_heart wrote:
Hi,
I have oracle 9.1 version and have created 5g undo tablespace apart from 20m rbs tablespace for 15 rollback segments. But it is seen that whenever i give UNDO_MANAGEMENT=AUTO then rollback segments are created using undo tablespace and not allowing rollback segment in rbs tablespace ONLINE. In the reverse happens whenever I give UNDO_MANAGEMENT=MANUAL , the rollback segments in the rbs tablespace gets focus and roll back segments in the Undo tablespace goes offline. Is there anything that I can do so that both undo tablespace and redo segments in the rbs tablespace gets working together so as to minimize the undo contention.No that's the way it would work, you can either use the automatic undo or the manual one.not both. And its better to stick with the automatic one IMHO. Have a read of this link to understand more about undo.
http://download.oracle.com/docs/cd/B10501_01/server.920/a96521/undo.htm#8888
HTH
Aman....

Undo tablespace currupt and no clean backup

Hello,
We are facing critical problem with database. We have not any clean backup and database in no archive log mode. Suddenly database is shutdown and when we are trying to open database it is giving error:-
ORA-01172: recovery of thread 1 stuck at block 350230 of file 3
ORA-01151: use media recovery to recover block, restore backup if needed
File 3 is Undo file.
Is there any way to open database?
Thanks in advance and please reply us ASAP.

1) First, follow Howardjr recomendations and allways do a backup first.
2) Open a SR with Metalink to help with your problem
3) If you want to try something here are some options, but never skip the point 1 previously explained.
Well, you have two possible scenarios, one supported other unsupported.
This is an inconsistency issue..
Solution
============
*1]Supported Solution:*
Restore-Incomplete recovery the DB from backup or rebuild the DB using an export dump.
*2]Internal (Not-supported) Solution:*
Update undo$ to change the status$ = 1 (undo segment is dropped) for the corrupted undo segment.
Caution:
This is NOT a supported solution. Therefore ensure that a full database cold backup is taken bbefore doing this data-dictionary patching.
Steps to do the patching:
1) First ensure that a full database backup is taken.
2) Modify/add the following parameters in initSID.ora:
undo_management=manual
job_queue_processes =0
aq_tm_processes=0
systemtrig_enabled=false
3) Shutdown
4) Startup restrict pfile
5) set transaction use rollback segment system;
if set transaction above fails, then not to proceed further.
6) Update undo$ to change the status$ = 1 (undo segment is dropped) for
the corrupt undo segment.
update undo$ set status$ = 1
where us# = <'undo segment id'>
and ts#=<'tablespace id'>
and file#=<'file id'>
and block# = <'block id'>
and status$=2;
or
update undo$ set status$ = 1
where name = <'corrupt undo segment name'>
and status$=2;
This will update only 1 row. Rollback the update if more than 1 row is updated.
7) Commit;
8) Shutdown abort
9) Set back in init.ora parameters modified in Step 2.
Startup restrict
10) Drop the corrupt undo tablespace using command:
drop tablespace <corrupt undo tablespace name> including contents;
11) Create new undo tablespace.
In initSID.ora, set undo_management=auto, undo_tablespace=<'new undo tablespace name'>
Restart the instance.
12) Take a backup.
*Parameter offlinerollback_segments is not useful:*
Trying to drop the corrupt undo segment or the undo tablespace by setting parameters undo management=manual and offline_rollback_segments in initSID.ora will fails with error: ORA-00600 [ktssdrp1].
To see the information about the corrupt block use this query:
select us#, name, ts#, file#, block#,status$ from undo$
where (ts#, file#, block#) not in
(select ts#, file#, block# from seg$ where type# in (1,10)) and status$ > 1;I had the same problem some time ago, and the unsupported solution works great, but never try it without a full backup first.
Cheers,
Francisco Munoz Alvarez
http://oraclenz.wordpress.com
Edited by: F.Munoz Alvarez on Nov 30, 2012 11:03 AM

UNDO tablespace resize/shrink.

Hi All ,
is it possible to shrink/resize undo tablespace.

Hi Shobhit!
I is correct that you're unable to set this parameter with ALTER SYSTEM. Please never use this parameter unless you are told to do so from oracle support. Maybe you're playing with your support if you set it by your self. To tune the size of your undo tablespace set the parameter undo_retention. Whit this parameter you tell your DB in seconds how long undo records should be kept within your undo tablespace. Automatic undotuning will be automatically activated if this parameter has a value greater than 0. To determine the correct size you need for your undotablespace use the following example:
Size of UNDO needed = UNDO_RETENTION x [UNDO block Generation per sec x DB_BLOCK_SIZE] + Overhead(30xDB_BLOCK_SIZE)
Out of these we know UNDO_RETENTION and DB_BLOCK_SIZE
All we need is to find out “UNDO Blocks per second”
Which can be easily fetched from v$undostat
SQL> SELECT (SUM(undoblks))/ SUM ((end_time - begin_time) * 24*60*60) "UPS"
2 FROM v$undostat;
UPS
8.11985583
V$undostat
stores data for every 10 mins and begin/end times are start/end time of
those intervals. We multiplied it with 24*60*60 because the difference
between two dates will be in days and to get to seconds, we need it to
multiply with 24hrs*60mins*60secs
So now we have all the values needed.
Undo size needed = [8.12 x 2000 x 8192] + [30 x 8192] = 133283840 bytes = 127.11 MB
Hope this helps!
yours sincerely

XE11: sysaux & undo tablespaces and files

Hello,
does anyone recognized the mixed names of sysaux and undo tablespaces?
If i use:
SQL> SELECT file_name, tablespace_name, ROUND(bytes/1024000) MB
SQL> FROM dba_data_files
SQL> ORDER BY 1;
then i will get:
FILE_NAME TABLESPACE MB
C:\ORACLEXE\APP\ORACLE\ORADATA\XE\SYSAUX.DBF UNDOTBS1 26
C:\ORACLEXE\APP\ORACLE\ORADATA\XE\SYSTEM.DBF SYSTEM 369
C:\ORACLEXE\APP\ORACLE\ORADATA\XE\UNDOTBS1.DBF SYSAUX 666
C:\ORACLEXE\APP\ORACLE\ORADATA\XE\USERS.DBF USERS 102
The file SYSAUX.DBF points to tablespace UNDOTBS1 and
the file UNDOTBS1.DBF points to tablespace SYSAUX
Could this cause a Problem ?
Can this be solved?
This is only in the windows-version, not in the linux-version.
Best reagrds
AK

Hello,
i did the following:
SQLPLUS:
SHUTDOWN IMMEDIATE;
AS ADMINISTRATOR:
COPY C:\oraclexe\app\oracle\oradata\XE\SYSAUX.DBF C:\oraclexe\app\oracle\oradata\XE\UNDOTBS2.DBF
COPY C:\oraclexe\app\oracle\oradata\XE\UNDOTBS1.DBF C:\oraclexe\app\oracle\oradata\XE\SYSAUX2.DBF
SQLPLUS:
STARTUP MOUNT:
ALTER DATABASE RENAME FILE 'C:\oraclexe\app\oracle\oradata\XE\SYSAUX.DBF' TO 'C:\oraclexe\app\oracle\oradata\XE\UNDOTBS2.DBF';
ALTER DATABASE RENAME FILE 'C:\oraclexe\app\oracle\oradata\XE\UNDOTBS1.DBF' TO 'C:\oraclexe\app\oracle\oradata\XE\SYSAUX2.DBF';
ALTER DATABASE OPEN;
SHUTDOWN IMMEDIATE;
AS ADMINISTRATOR:
COPY C:\oraclexe\app\oracle\oradata\XE\SYSAUX2.DBF C:\oraclexe\app\oracle\oradata\XE\SYSAUX.DBF (overwrite y)
COPY C:\oraclexe\app\oracle\oradata\XE\UNDOTBS2.DBF C:\oraclexe\app\oracle\oradata\XE\UNDOTBS1.DBF (overwrite y)
SQLPLUS:
STARTUP MOUNT:
ALTER DATABASE RENAME FILE 'C:\oraclexe\app\oracle\oradata\XE\SYSAUX2.DBF' TO 'C:\oraclexe\app\oracle\oradata\XE\SYSAUX.DBF';
ALTER DATABASE RENAME FILE 'C:\oraclexe\app\oracle\oradata\XE\UNDOTBS2.DBF' TO 'C:\oraclexe\app\oracle\oradata\XE\UNDOTBS1.DBF';
ALTER DATABASE OPEN;
SHUTDOWN IMMEDIATE;
AS ADMINISTRATOR:
DEL C:\oraclexe\app\oracle\oradata\XE\SYSAUX2.DBF
DEL C:\oraclexe\app\oracle\oradata\XE\UNDOTBS2.DBF
SQLPLUS:
STARTUP
RMAN:
REPORT SCHEMA;
Spooling started in log file: switch.txt
Recovery Manager11.2.0.2.0
RMAN>
Report of database schema for database with db_unique_name XE
List of Permanent Datafiles
===========================
File Size(MB) Tablespace RB segs Datafile Name
1 360 SYSTEM *** C:\ORACLEXE\APP\ORACLE\ORADATA\XE\SYSTEM.DBF
2 650 SYSAUX *** C:\ORACLEXE\APP\ORACLE\ORADATA\XE\SYSAUX.DBF
3 25 UNDOTBS1 *** C:\ORACLEXE\APP\ORACLE\ORADATA\XE\UNDOTBS1.DBF
4 100 USERS *** C:\ORACLEXE\APP\ORACLE\ORADATA\XE\USERS.DBF
List of Temporary Files
=======================
File Size(MB) Tablespace Maxsize(MB) Tempfile Name
1 20 TEMP 32767 C:\ORACLEXE\APP\ORACLE\ORADATA\XE\TEMP.DBF
RMAN>
Recovery Manager complete.
It's not looking elegant but it's working.
Is there a other way?
Best regards.

Dropping Undo Tablespace

Hi,
I am running Oracle 9.2 on Solaris. I have Automatic undo management turned on and have a Undo tablespace by name UNDOTBS. It has a single datafile and has AUTOEXTEND feature turned on. My UNDO_RETENTION was set to 4 hours.
Presently, the size of UNDOTBS has grown to around 40G and has filled up the file system in which it resides. I need to clean up the file system. In order to do this, I followed the below procedure.
SQL> create undo tablespace UNDOTBS1 datafile '/u04/oradata/proddb/undo_00.dbf' size 1024M autoextend off;
SQ> alter system set undo_tablespace=undotbs1 scope=both;
SQL> alter system set undo_retention=3600 scope=both;
Now, i checked the alert log and it is offlining all the UNDO segments of the first undo tablespace UNDOTBS. It is taking time and has been more than 1.5 hours. I have a couple of questions here,
1. As i have issued "alter system undo_tablespace=undotbs1 scope=both", all the new transactions will use the new UNDOTBS1. No new transactions will be using the first undo tablespace UNDOTBS right?
2. Since, i have issued "alter system undo_retention=3600 scope=both", all the transactions in first undo tablespace UNDOTBS will be rolled back after 2 hours, no matter if it is commited or not. After this period, i am safe to drop the first undo tablespace using "drop tablespace UNDOTBS including contents and datafiles;". Did i get it right?
Any information will be of a great help.
THanks,
Harris.

Hi,
Thank you all for the replies. It has been two days since i switched the undo_tablespace to use the new tablespace(undotbs1) but my alert log is still being flooded with " Undo tablespace 1 moved to pending switch out state". I tried the following to see if there are any rows returne from the above query and it did 3 rows, showing some undo segments with the following output
SQL> select a.name, b.status from v$rollname a, v$rollstat b where a.name in (select segment_name from dba_segments where tablespace_name='UNDOTBS') and a.usn=b.usn;
Name Status
_SYSSMU15$      UNKNOWN
_SYSSMU33$      UNKNOWN
_SYSSMU9$        PENDING OFFLINE
I have seen gone through the metalink id: 341372.1 that speaks about this SWITCH-OUT state. How can i make sure what old transactions are still using the Undo segments in first undo tablespace and how can i go about killing them. Could anyone please let me know that i could use the following queries to find the correct sessions that are using the Old Undo tablespace.
SQL> select ADDR, XIDUSN,STATUS, START_TIME from v$transaction;
SQL> SELECT
a.usn,
a.name,
b.status,
c.tablespace_name,
d.addr,
e.sid,
e.serial#,
e.username,
e.program,
e.machine,
e.osuser
FROM
v$rollname a,
v$rollstat b,
dba_rollback_segs c,
v$transaction d,
v$session e
WHERE
a.usn=b.usn AND
a.name=c.segment_name AND
a.usn=d.xidusn AND
d.addr=e.taddr AND
b.status='PENDING OFFLINE';
Just wanted to make sure that the second query lists the PENDING OFFLINE segments of the first tablespace right?
This is a prod. box, so wanted to confirm with you guys before proceeding.
Thanks,
Harris.

Segment shrinking and UNDO tablespace

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