Undo tablespace and instance recovery

Is UNDO tablespace is mandatory during instance recovery. ?
Suppose my undo tablespace has some active transaction and instance crashes making undo tablespace inaccessible.
Will database search for that undo tablespace during startup or I can simply create a new one and set as new undo tablespace ?
With Regards
Amt

Hi,
>>I am actually confused
Keep in mind that If an Oracle instance crashes, any changes that are made in the SGA are not written to the data files. When you restart the instance, the SMON background process automatically performs instance recovery by performing the following tasks:
• Rolling forward changes that are made in the online redo log files but not in the data files. Since all the committed transactions are written to the online redo log files, these are successfully recovered as result of rolling forward changes from the online redo log files to the data files.
• Opening the database. After the database is opened, users can log on and access any data that is not locked by un-recovered transaction.
• Rolling back all the uncommitted transactions.
In resume, during database recovery, undo records are used to undo any uncommitted changes applied from the redo log to the datafiles.
But if your UNDO tablespace crashed, then you will need recover it, using steps like
1) shutdown abort (If the instance yet is up)
2) cp -a /backup/undo01.dbf /u01/oradata (restore the latest recent backup file)
3) startup mount
4) recover database or recover datafile '/u01/oradata/undo01.dbf'
5) alter database open;
In some cases, re-create it, also resolve the problem:
http://asktom.oracle.com/pls/asktom/f?p=100:11:0::::P11_QUESTION_ID:5669213349582
Missing UNDO tablespace in restore backup
>>I checked in test setup and it is actually waiting for missing UNDO tablespace.
Which exactly test you are doing?
Cheers

Similar Messages

What is the difference between undo tablespace and online redo log files.

what is the difference between undo tablespace and online redo log files. I am confused
as per my knowledge undo tablespace is used to store the undo information when a table is being updated so that, just incase we need to rollback a transaction we know what was present in the table earlier.
when a transaction fails the SMON performs the rollback of the data.
This undo data is stored in the undo tablespace and read consistency if any is enforced.
is my understanding till here correct?
Now, can this undo data/before image not be stored in the redo log buffer and online redolog files?
can redo-log files not store this information?
in fact, is it that when undo tablespaces exist in a database, the undo data/before image is stored in both the undo tablespace and also the redo log files?
kindly clarify my doubt.
thank you.

This question has been asked many times before. The answer is always the same.
Yes, redo contains the before image of data (and the after-image). Therefore, it **COULD** be used to roll back a transaction.
BUT... Redo is written sequentially. Using it to rollback your transaction would involve reading through all the redo written by maybe thousands of other people. It would be painfully slow.
Your transaction is, however, directly linked to just the UNDO that it generates (which is JUST the before image of the data). So, your undo is your undo and doesn't share space with anyone else's undo. Therefore, using it to roll back YOUR transaction is fast.
The fact that undo is only the before image of the data also makes it faster than wading through a sea of before and AFTER images as you'd find in redo. About twice as fast, in fact, since there's half the data. Roughly.
Redo also gets written and flushed to disk whenever there's a commit, 3 seconds are up or too much (1MB, actually) redo gets generated between flushes caused by other factors. Your redo gets flushed when those things happen, even if you haven't actually committed your transaction. And redo logs recycle themselves, meaning that your redo -even if your transaction hasn't been committed yet- can be over-written by later transactions. Try rolling back when that's happened, if redo was the source of your rollback data!
Undo, however, cannot be over-written if the transaction has not been committed. Ever. If you don't commit for three years, there will be three years' undo stored in your database (assuming you had the space, of course!).
I could go on, but that will do. Redo is there fore RECOVERY, after catastrophe. Undo is there for read-consistency (and the occasional change of mind). Two different functions. Two different mechanisms. Each one highly tuned to doing what it does, why it does it, most efficiently and effectively.

Recovery lost undo tablespace and Redo log

Recovery undo tablespace
[email protected]> shutdown
Database closed.
Database dismounted.
ORACLE instance shut down.e
[email protected]> exit
Disconnected from Oracle9i Enterprise Edition Release 9.2.0.1.0 - Production
With the Partitioning, OLAP and Oracle Data Mining options
JServer Release 9.2.0.1.0 - Production
[ora920@tkyte-pc-isdn ora920]$ ls
control01.ctl cwmlite01.dbf indx01.dbf redo02.log redo0B.log temp01.dbf
users01.dbf
control02.ctl drsys01.dbf odm01.dbf redo03.log redo0C.log tools01.dbf
xdb01.dbf
control03.ctl example01.dbf redo01.log redo0A.log system01.dbf undotbs01.dbf
[ora920@tkyte-pc-isdn ora920]$ mv undotbs01.dbf undotbs01.dbf.xxx
[ora920@tkyte-pc-isdn ora920]$ sqlplus /nolog
SQL*Plus: Release 9.2.0.1.0 - Production on Sat Sep 28 08:33:29 2002
Copyright (c) 1982, 2002, Oracle Corporation. All rights reserved.
idle> connect / as sysdba
Connected to an idle instance.
idle> startup
ORACLE instance started.
Total System Global Area 143725064 bytes
Fixed Size 451080 bytes
Variable Size 109051904 bytes
Database Buffers 33554432 bytes
Redo Buffers 667648 bytes
Database mounted.
ORA-01157: cannot identify/lock data file 2 - see DBWR trace file
ORA-01110: data file 2: '/usr/oracle/ora920/OraHome1/oradata/ora920/undotbs01.dbf'
idle> show parameter undo
NAME TYPE VALUE
undo_management string AUTO
undo_retention integer 10800
undo_suppress_errors boolean FALSE
undo_tablespace string UNDOTBS1
idle> alter system set undo_management = manual scope=spfile;
System altered.
Note: disabling the undo tablespace here, this'll let us go back to "rollback segments"
and we'll use the system RBS to get back on our feet
idle> shutdown
ORA-01109: database not open
Database dismounted.
ORACLE instance shut down.
idle> exit
Disconnected from Oracle9i Enterprise Edition Release 9.2.0.1.0 - Production
With the Partitioning, OLAP and Oracle Data Mining options
JServer Release 9.2.0.1.0 - Production
[ora920@tkyte-pc-isdn ora920]$ !sql
sqlplus /nolog
SQL*Plus: Release 9.2.0.1.0 - Production on Sat Sep 28 08:35:34 2002
Copyright (c) 1982, 2002, Oracle Corporation. All rights reserved.
idle> connect / as sysdba;
Connected to an idle instance.
idle> startup
ORACLE instance started.
Total System Global Area 143725064 bytes
Fixed Size 451080 bytes
Variable Size 109051904 bytes
Database Buffers 33554432 bytes
Redo Buffers 667648 bytes
Database mounted.
ORA-01157: cannot identify/lock data file 2 - see DBWR trace file
ORA-01110: data file 2: '/usr/oracle/ora920/OraHome1/oradata/ora920/undotbs01.dbf'
Note: we still have to get rid of that thing..
idle> alter database datafile '/usr/oracle/ora920/OraHome1/oradata/ora920/undotbs01.dbf'
2 offline drop;
Database altered.
idle> alter database open;
Database altered.
idle> drop tablespace undotbs1;
Tablespace dropped.
idle> create UNDO tablespace undotbs1
2 datafile '/usr/oracle/ora920/OraHome1/oradata/ora920/undotbs01.dbf' size 25m
3 autoextend on next 1m maxsize 1024m;
Tablespace created.
idle> alter system set undo_management = auto scope=spfile;
System altered.
Now, we've put the undo tablespace "back" by creating a new one. Just bounce...
idle> shutdown
Database closed.
Database dismounted.
ORACLE instance shut down.
idle> exit
Disconnected from Oracle9i Enterprise Edition Release 9.2.0.1.0 - Production
With the Partitioning, OLAP and Oracle Data Mining options
JServer Release 9.2.0.1.0 - Production
[ora920@tkyte-pc-isdn ora920]$ !sql
sqlplus /nolog
SQL*Plus: Release 9.2.0.1.0 - Production on Sat Sep 28 08:40:51 2002
Copyright (c) 1982, 2002, Oracle Corporation. All rights reserved.
idle> connect / as sysdba;
Connected to an idle instance.
idle> startup
ORACLE instance started.
Total System Global Area 143725064 bytes
Fixed Size 451080 bytes
Variable Size 109051904 bytes
Database Buffers 33554432 bytes
Redo Buffers 667648 bytes
Database mounted.
Database opened.
idle> show parameter undo
NAME TYPE VALUE
undo_management string AUTO
undo_retention integer 10800
undo_suppress_errors boolean FALSE
undo_tablespace string UNDOTBS1
idle>
and we are right back where we started from
RECOVERY REDO TABLESPACE
STARTUP MOUNT;
RESTORE DATABASE;
RECOVER DATABASE UNTIL SEQUENCE $v_seq THREAD 1;
ALTER DATABASE OPEN RESETLOGS;

[email protected] wrote:
just ignore first one like title
Alter database open resetlog is not necessary to open database ?
Regards
kmphttp://download.oracle.com/docs/cd/B19306_01/backup.102/b14191/osrecov.htm#i1007426
About Opening with the RESETLOGS Option
The RESETLOGS option is always required after incomplete media recovery or recovery using a backup control file.
You did not do an incomplete media recovery nor a recovery using a backup control file.

Undo behavior during instance recovery

i'm confused about 2 concepts in applying undoin the case of instance failure
1.the common concepts of instance recovery which states :
a) when instance crash, oracle automatically applies all redo in the redo file to roll the db forward to the last scn be4 the failure
b) & redo data also contains the undo data, it also undo the uncommitted changes from the old valuesin the undo.
that'sok
2.but refereing to 10g database concepts (ch17 high availability-p317 if pdf)
url: http://download-uk.oracle.com/docs/cd/B19306_01/server.102/b14220/high_av.htm#sthref2531
it says:
With fast-start fault recovery, the Oracle database is opened for access by applications without having to wait for the undo, or rollback, phase to be completed.
The rollback of data locked by uncommitted transaction is done dynamically on an as needed basis.
If the user process encounters a row locked by a crashed transaction, then it just rolls back that row.
The impact of rolling back the rows requested by a query is negligible.
Fast-start fault recovery is very fast, because undo data is stored in the database, not in the log files.
Undoing a block does not require an expensive sequential scan of a log file.
so which situation is applicable in case of instance recovery
& do the undo behvior stated above in case of fast start fault recovery is an option or that's the default
thnx alot

Hi,
Whatever changes are made to the database, are recorded in redo log buffer cache sequentially and then shifted to redo log files. Suppose redo logs recorded following changes in the database in following sequence.
insert a row
update a row
commit;
delete a row
Now Instance crashes before these changes were written into the database (data remains in buffer cache until checkpoint)
Now during instance recovery, data which was still in buffer cache and not written to the data files, will be applied in same sequence. All undo data for update/delete is in redo log files and will be applied in the same sequence.
Salman

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.

Undo Tablespace and Temporary Tablespace - autoextend ?

- In general, should I allow the Undo Tablespace to grow (autoextend)?
- In general, should I allow the Temporary Tablespace to grow (autoextend)?

The size of undo tablespace should always keeps in mind otherwiase you eill get ORA-1555 or out of space errors.
This paper is to help DBA’s in calculating the size of UNDO tablespace by using a simple formula.
It is tough to know about the number of transactions and subsequently number of rows changed per second.
So I suggest having a “big undo tablespace” to start with and based on load, after doing some calculations and resize your UNDO tablespace.
In my case one of the applications was going to production (live), and I had no idea that how many transactions will happen against this database. All what I was told that there will be optimum (transactional) activity on this database.
So I started with UNDO tablespace with size of 3GB and datafiles with autoextend “on” .
Note:
In production, you must be very careful in using this (autoextend on) as the space may grow to inifinity very fast. So my advice is either dont use this option, or use with "maxsize" or continuously monitor space (which is tough).
I month later, I noticed the activity from V$undostat.
Here is the step by step approach:
Step 1: Longest running query.
SQL> select max(maxquerylen) from v$undostat;
MAX(MAXQUERYLEN)
1793
This gives you ideal value for UNDO_RETENTION. To be on the safer size you should add few more seconds to get the right value. So in my case, the size of undo retention should be say 2000 secs.
Step 2: Size of UNDO tablespace.
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

CheckPoint and Instance Recovery

hi,
what is checkpoint Exactly.How it will Preform Instance Recovery.
thanks
with Regards

hi,
thanks for reply.I read the documents and books,but i am not clear Exact point so that i have been posting here.
for example
semantic checking
Twq User a,b.Both of them has Emp tables but different Columns.
user A
select * from Emp;
User B
select * from Emp;
here i have doubts after B executing the query. how oracle take this, i think is it Semantic.
I am n't going to learn without Meaning a single word....
some terms not understanding so i am posting here
thanks
with regards

Undo tablespace and hotbackup

if we dont back up UNDO table space on a hot backup situation, will we have any issues while recovering that database..

Yes.. Undo + system tablespace are very important while recovery
--Girish

Dropping the 4th undo tablespace, 4th thread from a 3 instance database

I migrated a 4 instance RAC database from a 4 node server to a 3 node RAC database server. However, I still have the 4th undo tablespace and the 4th redo log thread. Are there any precautions I need to take before dropping the 4th undo tablespace? Must I also drop the 4th redo log thread, or will the database function properly even without a 4th node to go with the 4th thread?
I presume I have to also disable the 4th public thread? Is this the command below?
Alter database disable public thread=4;

I guess it does not matter that group 12 in thread 4 is "CURRENT" since the thread is not being used. But I don't believe I can drop a "CURRENT" group, can I?
SQL> select group#, thread#, bytes, members, status from v$log;
    GROUP#    THREAD#      BYTES    MEMBERS STATUS
         1          1   52428800          2 CURRENT
         2          1   52428800          2 INACTIVE
         3          1   52428800          2 INACTIVE
         4          2 104857600          2 INACTIVE
         5          2 104857600          2 INACTIVE
         6          2 104857600          2 CURRENT
         7          3   52428800          2 INACTIVE
         8          3   52428800          2 INACTIVE
         9          3   52428800          2 CURRENT
        10          4   52428800          2 INACTIVE
        11          4   52428800          2 INACTIVE
        12          4   52428800          2 CURRENT
12 rows selected.

Undo tablespace full even with no active transaction and undo_retention 10s

The 9.2.0.4 instance is AUM (auto undo management). The undo table space is 50G and is almost full.
I have set the undo_retention to 10, previously it was 10800 (3hours). I restart the database. Wait quite long time.
And search on the dba_undo_extents.
select sum(bytes/(1024*1024*1024)),status from dba_undo_extents d where d.tablespace_name='UNDOTBS2' group by status;
SUM(BYTES/(1024*1024*1024)) STATUS
.574447632 EXPIRED
45.5358887 UNEXPIRED
It is hard to explain. 10 seconds already passed, at least all the extents should be expired.
Why so many 45G is still unexpried.
Is there a bug for undo tablespace? how to fix it.
It is a rac instance, I am trouble shooting the undo tablespace issues.
The UNDOTBS2 is for node2 to use.

If you start the database in exclusive (one instance) mode then the database instance can have only one undo tablespace so I would not expect Oracle to do anything with the undo tablespace for the non-running instance.
Run you database as normal and generate undo. See if the status changes. If if does that would imply that Oracle does not expire undo unless the undo segments (rbs segments) are accessed. Please post back with results of what you see.
Between having batch production running on all my databases that use undo tablespaces and the fact we use uniform extent undo tabllespaces I am not in a position to try to duplicate what you are seeing.
HTH -- Mark D Powell --

Partial Recovery - Skip UNDO Tablespace

Hi,
I was performing a partial database recovery using skip tablespace option using RMAN. I was wondering if I can skip undo tablespace.
I was not able to conclude whether I can do that? If not, why?
As per my understanding,
1. Datafiles are restored - If they have any uncommited data, then archive logs which will be applied for media recovery, will have the undo data to perform those roll backward.
2. While performing media reccovery using archive logs, it will generate it's own undo data.
Why do we need the stale undo data (generated till datafiles restoration point)?
Thanks,
Janak Agrawal

Soli,
Thread that you have specified, talks about datafiles which does not have any uncommitted data (As the database was normally shutdown). In this case, we can drop and recreate the undo tablespace.
But I am talking about a past point-in-time recovery using RMAN, where the datafiles which will be restored may have the uncommitted data. To rollback these uncommited trnasactions, will we have data in next archivelogs, which will be used for media recovery or the data (needed to rollback) will have only in undo tablespace. Let me give you an example.
At 9 am I want to restore the datbase till 8.15 AM. Full backup is available till 8 AM and then from 8 to 8:15 arvhive logs are available. While doing recovery, datafiles will be restored till 8 AM. If at 8 AM there is some uncommitted data in datafiles, will it require data from undo tablespace to rollback or first archive log after 8 AM w'd take care of roll back? If archive logs can take care of rollback, why can't I skip the undo tablespace while doing recovery?
Santosh,
As you mentioned, UNDO data will require for read-consistency. But the same data will be available in archive logs (which will require after datafiles restore) which can generate their own UNDO data.
Please clarify. I am sorry if I am missing anything here.
Thanks,
Janak Agrawal

Is there so call "dedicated" UNDO tablespace in Oracle 9i and higher?

Since one of our applicaions needs to process large amounts of data, we have been using a dedicated rollback segment in order to avoid the "snapshot too old" problem.
Recently our DB upgraded to Oracle 9i and DBA asked us to use "undo" tablespace.
Based the Oracle 9i Doc., it only allows to select ONE undo tablespace at a time.
If so, DBA has to make the only UNDO as large as our Cash large transactions
need(adjust the UNDO_RENTION), which inevitably waste lots of space.
Does Oracle 9i allow to have one dedicated UNDO tablespace for large transactions while another one for regular transactions just like we use the old rollback segments.
Thanks in advance

Why have multiple UNDO tablespaces? You can only use one at a time, and when the other one is not being used, it still consumes storage space.
Spend a little time determining how much undo you need and size undo tablespace and undo retention around those values and you should be able to resolve the problems you are experiencing now.
http://download-east.oracle.com/docs/cd/B10501_01/server.920/a96521/undo.htm#9505

Cacluation of undo tablespace size and retenion

How to calaculate the expected size of the undo tablespace and undo retention parameter from the exisitng data.

The easiest way to calculate undo requirementes is using the undo advisor, it is available in 10g and 9i. This is a graphical tool that lets you know the amount of required undo space according to your generated undo data.
Regards.

Open XE without UNDO tablespace

Hy
I have an oracle xe installation on linux ubuntu that does not start, it arrives in MOUNT status.
When i try to open i get the following messages:
ORA-01172: recovery of thread 1 stuck at block 153 of file 2
ORA-01151: use media recovery to recover block, restore backup if needed
Unfortunately it is in NOARCHIVELOG mode.
Can i open it with no UNDO tablespace, and the add a new datafile to the UNDO tablespace?
Thanks
Lorenzo

Here is alert log content: the last shutdown was not clean
Here there is not the shutdown log...
Tue Mar 9 17:42:29 2010
starting up 4 shared server(s) ...
Oracle Data Guard is not available in this edition of Oracle.
Tue Mar 9 17:42:31 2010
ALTER DATABASE MOUNT
Tue Mar 9 17:42:35 2010
Setting recovery target incarnation to 2
Tue Mar 9 17:42:35 2010
Successful mount of redo thread 1, with mount id 2594312135
Tue Mar 9 17:42:35 2010
Database mounted in Exclusive Mode
Completed: ALTER DATABASE MOUNT
Tue Mar 9 17:42:35 2010
ALTER DATABASE OPEN
Tue Mar 9 17:42:35 2010
Beginning crash recovery of 1 threads
Tue Mar 9 17:42:35 2010
Started redo scan
Tue Mar 9 17:42:36 2010
Completed redo scan
1264 redo blocks read, 136 data blocks need recovery
Tue Mar 9 17:42:36 2010
Started redo application at
Thread 1: logseq 175, block 2, scn 6715755
Tue Mar 9 17:42:36 2010
Recovery of Online Redo Log: Thread 1 Group 2 Seq 175 Reading mem 0
Mem# 0 errs 0: /usr/lib/oracle/xe/app/oracle/flash_recovery_area/XE/onlinelog/o1_mf_2_5dm8sg16_.log
RECOVERY OF THREAD 1 STUCK AT BLOCK 153 OF FILE 2
Tue Mar 9 17:42:37 2010
Aborting crash recovery due to error 1172
Tue Mar 9 17:42:37 2010
Errors in file /usr/lib/oracle/xe/app/oracle/admin/XE/udump/xe_ora_4250.trc:
ORA-01172: recovery of thread 1 stuck at block 153 of file 2
ORA-01151: use media recovery to recover block, restore backup if needed
ORA-1172 signalled during: ALTER DATABASE OPEN...

Is it OK to Switching Undo Tablespaces without DB stop ?

We use Oracle11g R2.
I read Oracle Doc and It looks OK.
But, how could I make sure UNDO tablespace mode(ONLINE,PENDING OFFLINE) ?
Switching Undo Tablespaces
You can switch from using one undo tablespace to another. Because the UNDO_TABLESPACE initialization parameter is a dynamic parameter, the ALTER SYSTEM SET statement can be used to assign a new undo tablespace.
The following statement switches to a new undo tablespace:
ALTER SYSTEM SET UNDO_TABLESPACE = undotbs_02;
Assuming undotbs_01 is the current undo tablespace, after this command successfully executes, the instance uses undotbs_02 in place of undotbs_01 as its undo tablespace.
If any of the following conditions exist for the tablespace being switched to, an error is reported and no switching occurs:
The tablespace does not exist
The tablespace is not an undo tablespace
The tablespace is already being used by another instance (in an Oracle RAC environment only)
The database is online while the switch operation is performed, and user transactions can be executed while this command is being executed. When the switch operation completes successfully, all transactions started after the switch operation began are assigned to transaction tables in the new undo tablespace.
The switch operation does not wait for transactions in the old undo tablespace to commit. If there are any pending transactions in the old undo tablespace, the old undo tablespace enters into a PENDING OFFLINE mode (status). In this mode, existing transactions can continue to execute, but undo records for new user transactions cannot be stored in this undo tablespace.
An undo tablespace can exist in this PENDING OFFLINE mode, even after the switch operation completes successfully. A PENDING OFFLINE undo tablespace cannot be used by another instance, nor can it be dropped. Eventually, after all active transactions have committed, the undo tablespace automatically goes from the PENDING OFFLINE mode to the OFFLINE mode. From then on, the undo tablespace is available for other instances (in an Oracle Real Application Cluster environment).

After you switch the UNDO_TABLESPACE parameter to the new tablespace, at the minimum, you have to wait for active transactions to complete (commit/rollback) before you can take the old Undo Tablespace offline. Note that if you take the old Undo Tablespace offline too quickly, you may prevent long running queries from reading from the old Undo Tablespace and may cause them to error with ORA-01555. So you need to wait a reasonable time (e.g look at MAXQUERYLEN in V$UNDOSTAT) before you take the old Undo Tablespace offline.
Hemant K Chitale

Undo tablespace and instance recovery

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