Snapshot too old ORA-01555 from select statement (discoverer)??

Hi All
Am I loosing the plot .. but we have a select statement run from discoverer which is causing the famous snapshot too old error.
My understanding is that undo is generated from select/insert/update.
So why is the following discoverer Select statement causing the error?
from alert
ORA-01555 caused by SQL statement below (SQL ID: gk0wxgqmx66sh, Query Duration=3866 sec, SCN: 0x001e.089cf3f9):
SELECT ( ROUND(( TO_DATE(SYSDATE)-o101038.HIRE_DATE )/365,2) ) as
" bla bla
ORDER BY o101020.SUB_ORGANIZATION_NAME ASC
Thanks in Advance

simon.9999 wrote:
Hi All
Am I loosing the plot .. but we have a select statement run from discoverer which is causing the famous snapshot too old error.
My understanding is that undo is generated from select/insert/update.
So why is the following discoverer Select statement causing the error?
from alert
ORA-01555 caused by SQL statement below (SQL ID: gk0wxgqmx66sh, Query Duration=3866 sec, SCN: 0x001e.089cf3f9):
SELECT ( ROUND(( TO_DATE(SYSDATE)-o101038.HIRE_DATE )/365,2) ) as
" bla bla
ORDER BY o101020.SUB_ORGANIZATION_NAME ASC
Thanks in Advance
The SELECT statement is the victim.
Some session is doing DML against the same table against which the SELECT occurs & is likely doing COMMIT inside a LOOP.

Similar Messages

Snapshot too old when deleting from a "big" table

Hello.
I think this is a basic thing (release 8.1.7.4). I must say I don't know how rollback segments really work.
A table, where new records are continuously inserted and the old ones can be updated in short transactions, should be purged every day by deleting old records.
This purge has never been done and as a result it has now almost 4 million records, and when I launch the stored procedure that deletes the old records I get the "snapshot too old" error because of the read consistency.
If I launch the procedure after stopping the application that inserts and updates in the table, then I don't get the error. I guess the problem is that meanwhile the procedure is being executed other transactions also need to use rollback segments so that the rollback segment space that the snapshot needs isn't enough. Do you think this is the problem?
If this is the case then I suppose that the only solution is increasing the size of the only datafile of the only tablespace for my 4 rollback segments. Am I wrong?
(Three more questions:
- Could the problem be solved by locking some rollback segments for the snapshot? How could I do that?
- What is a discrete transaction?
I'm a developer, not a dba, but don't tell me to ask my dba because it isn't that easy. Thanks in advance.

"snapshot too old indicates the undo tablespace does not have enough free space for a long running query" what does this mean? why do I get the same error in two different databases, in the first the size of the datafile of the undo tablespace is 2GB whilst in the second it is only 2MB? How can I know how big the datafile has to be?
One possible solution could be not deleting the whole table at once but only a few records? Would this work? Why when I try "select count(*) from my_table where rownum = 1" I also get "snapshot too old" when other transactions are running.

Snapshot too old error - disambiguation required.

[http://asktom.oracle.com/pls/asktom/f?p=100:11:0::::P11_QUESTION_ID:275215756923]
It is known that Oracle provides row-level locks, meaning, two different transactions can update two different rows,
1. Is this true even if they reside in the same block?
2. If yes, as per the reasons stated in the above reference, Oracle should not find that the block has been modified for that particular, different, row. I am baffled at this point.
Resue needed.
Thanks in adv.
Aswani V.

if your concern is abou snapshoot too old (ora-01555) error, you know the reason for this undo tablespace size and the length of the longest running query. If you need to be able to get consistent read version of the block, which is needed for your long running query(which raises snapshot too old error), you have two options. 1) you can increase the size of your undo tablespace and find the optimum size considering your pick workload and longest running query. I mean your undo tablespace size should be enough to hold the undo data generated during the peak workload and provide read consistent version of the block for your longest running query. Again, it does not guarantees snapshot tooo old error could not happen. 2) in the second choise, you can change your undo tablespaces for guaranteed retention. In this case, despite the time of running of your longest query, you will not get snapshot too old errors. But, it measn that, during the heavy workload period, you can get errors with transactions which involve DML operations, if they could not find enough space for UNDO. So, i would increase the size of Undo tablespace and measure if it is ok or not. Oracle itself smartly choses which undo data is gonna be overwritten, even in the case of noguarantee undo tablespace. I.e. it will not overwrite the read consistent versions of undo blocks if there is some free(or expired) undo blocks.

ORA-01555: snapshot too old

Hi,
We have audit component, one responsibility of which is to archive audit messages from Oracle database. The component fails on a simple select statement (provided below) that retrieves number of records to be archived based on age parameter:
SELECT COUNT(*) FROM blobobjtable blbt, auditmessagetable msgt WHERE msgt.blobobjtablepk = blbt.blobobjtablepk AND trunc(to_number(substr((SYSTIMESTAMP-msgt.credtimeutc),1,instr(SYSTIMESTAMP-msgt.credtimeutc,' ')))) >= age
We tried the following 3 select statements directly from SQL Plus. The result was that the first two succeeded and the last one failed with "ORA-01555: snapshot too old" exception. We tried these select statements after restart of Oracle database but still got last select statement failed. One thing that we noticed was that the last select statement takes extremely long time to complete. Also, analyzing the index table used during the join failed with the same exception. The same is true when the primary key indices are analyzed.
1) select count(*) from blobobjtable
2) select count(*) from auditmessagetable
3) select count(*) from blobobjtable blbt, auditmessagetable msgt WHERE msgt.blobobjtablepk = blbt.blobobjtablepk
Can somebody explain what might be the cause of ORA-01555 exception for such simple select statement? Does Oracle persists information of UNDO buffers before restart? Is there any way to clean UNDO buffers manually?
If somebody has experience in resolving "ORA-01555: snapshot too old" exception problem please share you experience with us. Any help will be appreciated.
Thanks,
Aleks

how many rows in ur tables.
select count(*) from blobobjtable blbt
SQL> show parameter undo
NAME                                 TYPE        VALUE
undo_management                      string      AUTO
undo_retention                       integer     300
undo_tablespace                      string      UNDOTBS1
SQL> select count(*) from sm;
COUNT(*)
   1326661
Elapsed: 00:00:03.53
SQL> select count(*) from sm;
COUNT(*)
   1326661
Elapsed: 00:00:03.45
SQL> select count(*) from sm ss,ac_taj@taj ac
2 where ss.nserial = ac.nserial;
COUNT(*)
     88763
Elapsed: 00:00:38.35
SQL> show parameter db_name
NAME                                 TYPE        VALUE
db_name                              string      db02
SQL>i have some configuration of undo tbs. but i am not getting any error. also i am just startup my database if right know i am only one user connected to database.
SQL> select bytes/1024/1024 "UNTO MB" from dba_data_files
2 where tablespace_name = 'UNDOTBS1'
3 /
   UNTO MB
       930

Receiving error ORA-01555: snapshot too old:

Need some info...
Currently seeing ORA-01555: snapshot too old: rollback segment number 18 with name "_SYSSMU18$" too small.
Info:
SQL> show parameter undo
NAME TYPE VALUE
undo_management string AUTO
undo_retention integer 4200
undo_suppress_errors boolean FALSE
undo_tablespace string UNDOTBS_1
SQL> select max(maxquerylen) from v$undostat;
MAX(MAXQUERYLEN)
35792
SQL>
run this based on threads in here:
SQL> select (35792/60)/60 query,(4200/60)/60 retention from dual;
QUERY RETENTION
9.94222222 1.16666667
I need some help figuring out what to set my undo_retention to? Should it be 36000?
Any help is appreciated.
Thanks

Jamie CC wrote:
The query that was in the alert log was running against a table with 779 rows. The query uses the index (not worried if it wouldn't for that small a table) and came back in one second... This makes no sense. Is it possible that there was a sub-query running and the wrong query was put into the alert log?More likely the query in the alert log was one that died, but the cause was a different query. Remember, the meaning of an ORA-1555 is that the query needed to go back to undo in order to gather a view of the data to a certain SCN, and the data had already been aged out. So the alert log gets the one that died, but the cause is another one. Feel lucky at that, in older versions it was considered an app error IIRC.
Search for the error on asktom.oracle.com for a number of scenarios, and you might want to review the part of the concepts manual about read consistency to make sense of it all. You might also find Tom's book explanation about it with a google search.
Also, depending on your version, there may be things to set like retention guarantee.
I've found on the ERP/MRP systems I work on these errors will appear weekly from people leaving sessions connected after they go home, so I kill 'em off at night. And that's with an undo nearly as big as the db data, that's normally almost empty.

ORA-01555: snapshot too old while creating large index

Dear All,
I have a newly created partitioned table of size 300GB.
On which i am creating a composite unique index having 5 columns(local partitioned).
The size of the index may be around 250GB(assume from a similar type table).
My DB version in Oracle 9i release 2.
Size of my undo tablespace is 12GB.
Undo related parameters are as below:
undo_management AUTO
undo_retention 18000
undo_suppress_errors FALSE
At 10:40:36 AM i fired the "create index .... local;" query
All day long i was monitoring using "select used_ublk,addr from v$transaction" and same below output all the times:
USED_UBLK ADDR
1 C000000185ECF458
[ using v$session(column TADDR) i found that "C000000185ECF458" is the ADDR of my transaction (if i am not wrong) ]
But at 11:09:27 PM (about 12 hours later) i found: ORA-01555: snapshot too old
I am sure that at that time my undo tablespace usages was below < 30%
At that time some insertion & selection was going on but those were not on this table.
Why this happened ? As far as i know oracle in AUM oracle doesn't overwrite existing undo data as long as there
is free space available.
While searching on web i found one post as below:
like

Thanks guys for your prompt replys.
Yes i've monitored v$TEMPSEG_USAGE and DBA_SEGMENTS for the progress of the index creation, but this are not related to my question and yes i could use nologging or parallel (in gact i'm going to try all these options for faster index creation). On my original post i missed below part, please go through it:
While searching on web i found one post as below:
metalinknote #396863.1 which describes it
=> 2) When are UNDO segments OFFLINED?
Answer:
SMON decides on the # of undo segs to offline and drop based on the max transaction concurrency over a 12 hour period in 9i. This behavior is altered in 10g where the max concurrency is maintained over a 7-day period. Moreover, in 10g SMON doesn't drop the extra undo segs, but simply offlines them. SMON uses the same values with "fast ramp up" to adjust the number of undo segments online.
Link:[http://kr.forums.oracle.com/forums/thread.jspa?threadID=620489]
I says "SMON decides on the # of undo segs to offline and drop based on the max transaction concurrency over a 12 hour period in 9i.".
what does it mean ? Is this the cause for me, as my query war 12 hours old and my undo_retention is set to 5 hours ?
I'll be very grateful if some one explains the cause.
BR
Obaid

ORA-01555: snapshot too old: rollback segment number 8 with name

Hi,
Database version is Oracle8i Enterprise Edition Release 8.1.7.4.0
I am struggling to fix this error, since I have not worked on 8I DATABASE.
We getting this kind of error very frequently in one of the 8i database.
ORA-01555: snapshot too old: rollback segment number 8 with name "ROLLBACK08" too small
How do i fix this permantely.
I have verified the RBS configured in the db.
SEGMENT_NAME TABLESPACE_NAME OWNER STATUS
SYSTEM SYSTEM SYS ONLINE
ROLLBACK0 SYSTEM SYS OFFLINE
ROLLBACK02 RBS1 SYS ONLINE
ROLLBACK03 RBS1 SYS ONLINE
ROLLBACK04 RBS1 SYS ONLINE
ROLLBACK05 RBS1 SYS ONLINE
ROLLBACK06 RBS1 SYS ONLINE
ROLLBACK07 RBS1 SYS ONLINE
ROLLBACK08 RBS1 SYS ONLINE
ROLLBACK09 RBS1 SYS ONLINE
ROLLBACK10 RBS1 SYS ONLINE
ROLLBACK01 RBS1 SYS ONLINE
SQL> SELECT t1.name, t2.extents, t2.rssize, t2.optsize, t2.hwmsize, t2.xacts, t2.status FROM v$rollname t1, v$rollstat t2 WHERE t2.usn = t1.usn ;
NAME EXTENTS RSSIZE OPTSIZE HWMSIZE XACTS STATUS
SYSTEM 7 770048 770048 0 ONLINE
ROLLBACK02 2 41934848 262144000 41934848 0 ONLINE
ROLLBACK03 3 62906368 262144000 62906368 1 ONLINE
ROLLBACK04 3 62906368 262144000 62906368 0 ONLINE
ROLLBACK05 2 41934848 262144000 41934848 0 ONLINE
ROLLBACK06 3 62906368 262144000 62906368 1 ONLINE
ROLLBACK07 3 62906368 262144000 62906368 1 ONLINE
ROLLBACK08 3 62906368 300146688 62906368 0 ONLINE
ROLLBACK09 3 62906368 262144000 62906368 1 ONLINE
ROLLBACK10 3 62906368 262144000 62906368 1 ONLINE
ROLLBACK01 3 62906368 300146688 62906368 0 ONLINE
NAME0     USER0          RSSIZE Wraps Extents Shrinks     OPTSIZE     COMM0
ROLLBACK01          62906368     19     3     0 300146688 lookup
ROLLBACK02          41934848     0     2     0 262144000 lookup
ROLLBACK03 OPS$RTRADM     62906368     20     3     0 262144000 lookup 50
ROLLBACK04          62906368     34     3     0 262144000 lookup
ROLLBACK05 OPS$RTRADM     41934848     28     2     0 262144000 No Command
ROLLBACK06 OPS$RTRADM     62906368     21     3     0 262144000 lookup 50
ROLLBACK07 OPS$RTRADM     62906368     25     3     0 262144000 lookup 50
ROLLBACK08          62906368     32     3     0 300146688 lookup
ROLLBACK09 OPS$RTRADM     62906368     20     3     0 262144000 Select
ROLLBACK10 OPS$RTRADM     62906368     24     3     0 262144000 lookup 50
SYSTEM               770048     0     7     0     lookup
Can someone help ... who to set the RBS size here... i dont want this error happens here.. what i need to look or check.

lm**** wrote:
Hi,
Database version is Oracle8i Enterprise Edition Release 8.1.7.4.0
I am struggling to fix this error, since I have not worked on 8I DATABASE.
We getting this kind of error very frequently in one of the 8i database.
ORA-01555: snapshot too old: rollback segment number 8 with name "ROLLBACK08" too small
How do i fix this permantely. upgrade to supported Oracle version since V8.1.7 has not been supported this Century.

ORA-01555: snapshot too old / set transaction

Hello,
When I execute a query in a script I have the following error: ORA-01555: snapshot too old...
At the beginning of the script I have SET TRANSACTION use rollback segment XX.
On the other hand I used SET TRANSACTION READ ONLY and I had no errors.
It is a fate or it is the solution?
What is the difference?
Thanks

It's probably just fate. SET TRANSACTION READ ONLY guarantees a read consistent view during the whole transaction rather than an individual statement, but it is not a sovereign remedy against ORA-1555.
SET TRANSACTION USE ROLLBACK SEGMENT XXXX is meaningless in the context of a SELECT only transaction.
The ORA-1555 is casued by someone else doing DML that the rollback segment holding the undo information that Oracle uses to provide read consistency. The way to prevent it is to manage the rollback segments properly - big, numerous, high minextents, no shrinking - or to use 9i UNDO tablespace instead.
Cheers, APC

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

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

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

ORA-01555: snapshot too old error

While i was trying to run the following anonymous block to analyze all the tables and indexes in my schema, it ran for approx. 5 hours and ended up with
ORA-01555: snapshot too old error
Can anybody explain me why this happened?
SQL> DECLARE
2 CURSOR tab_cur
3 IS
4 SELECT table_name
5 FROM user_tables;
6
7 CURSOR indx_cur
8 IS
9 SELECT index_name
10 FROM user_indexes;
11 BEGIN
12 FOR rec IN tab_cur
13 LOOP
14 EXECUTE IMMEDIATE 'ANALYZE TABLE '
15 || rec.table_name
16 || ' COMPUTE STATISTICS';
17 END LOOP;
18
19 FOR rec IN indx_cur
20 LOOP
21 EXECUTE IMMEDIATE 'ANALYZE INDEX '
22 || rec.index_name
23 || ' COMPUTE STATISTICS';
24 END LOOP;
25 END;
26 /
DECLARE
ERROR at line 1:
ORA-01555: snapshot too old: rollback segment number 13 with name "_SYSSMU13$"
too small
ORA-06512: at line 12
Elapsed: 05:01:26.08
Thanks and Regards
--DKar

Your cursor loop uses the database catalog.
The analyze updates the database catalog -- including some of the same tables required by the cursor loop.
The undo retention was not sufficient to hold all of the undo necessary to maintain read consistency of the catalog.
Try using something like this, instead.
-- for 9i
BEGIN
DBMS_STATS.GATHER_SCHEMA_STATS (
          ownname               => '<YOUR SCHEMA>',
          estimate_percent      => DBMS_STATS.AUTO_SAMPLE_SIZE,
          block_sample          => TRUE,
          method_opt            => 'FOR ALL COLUMNS SIZE AUTO',
          degree                => 6,
          granularity           => 'ALL',
          cascade               => TRUE,
          options               => 'GATHER'
END;

Why ORA-01555 (Snapshot too old) occures on an unchanged table

Hello,
we have to add a not null column into a large table. The simple update is not good, due to UNDO space.
alter table T add F INTEGER default 0 not null;
ORA-30036: unable to extend segment by in undo tablespace ''It is OK. (We cannot use create + insert + drop + rename due to not enough free space. The table is not partitioned current) So we try this script:
--create the column without default and not null
alter table T add F INTEGER;
--create temp table with the rowids of T (nologging -> minimal log)
create table TMP (row_id rowid) nologging;
--save the rowid-s. (direct -> minimal undo usage)
insert /*+APPEND*/ into TMP(row_id) select rowid from T;
commit;
--the "insert method"
--set the column to "0" with frequently commit
declare
i integer := 0;
commit_interval integer := 10000;
begin
for c in (select * from TMP) loop
    update T set F=0 where rowid=c.row_id;
    i := i + 1;
    if( mod(i,commit_interval)=0) then commit;
    end if;
end loop;
commit;
end;
--set to not-null
alter table T modify F default 0 not null;
--drop the temp table
drop table TMP;the insert method occures
ORA-01555: Snapshot too old (in row 5)The row 5 is the cursor "select * from TMP" in the insert method. The undo usage of this method is below 2 MB.
My question is:
Why oracle need snapshot, while the TMP table does not change during the insert method? The TMP table was populated and commited before the insert method. Why oracle try to read the rows of the TMP table from the undo tablespace?
Thx: lados.

Thank, I have read this article, but there is something, what I don't understand.
As I see, the DML does not clear all the modified datablock header, but it clears only the rollback segment slots. Only the next SQL (even if this is a query) clears the datablock header. This next SQL can clear only when the info is still available in the rollback segment, else ORA-1555 occures.
My question is:
What happens when the next SQL comes only one year later on this block? I don't believe that oracle doesn't handle this situation, but I didn't find how it is handled.
Thx: lados.

The nature of "ORA-01555: snapshot too old..." error

Hi all,
Please help me to understand the nature of this error:
ORA-01555: snapshot too old: rollback segment number 23 with name "_SYSSMU23_755263746$" too small
One of reports returns this error. Yes, I googled it, but honestly I can't understand deeply what causes it. Usually I resolve it by performing sql request on yesterday's copy of production database. Is it correct to say that this error happens when I try to perform request on tables that are changed in the same moment? What is correct solution to resolve it other than using yesterday's copy of production database?

marco wrote:
Antonio,
The problem is generally small segments of undo, you need to add more space or put guaranty the tablespaces.
How do I describe it for our DBA (how much extra space do I need and what is the name of tablespace)?
Before you go to your DBA, you should figure out how much space your largest query/update uses. That is, your biggest transaction, how much space does it need? 10M? 100M? 1G? From there, your DBA can then size your UNDO properly (or at least "more better" ). Yes he "name of the tablespace" is just called "UNDO").
As mentioned before, the solution might not even be to increase your UNDO size, but rather to identify the "problem job", and fix it. That's not easy, however, talk to your DBA, he may be able to help with that as well.
Things to look for:
1) a job that issues a lot of commits. (suspicious - try to reduce # of commits).
2) a job that runs for a long time and updates along the way (suspicious - try to reduce run time).
3) a job that runs for a long time and has no updates (try to reduce run time - in this case, if this job starts running, and then takes a long time, a lot of other jobs may be reasonably doing updates, and this long run query needs to reference a row that was updated - it might lose it in the UNDO, though).
4) long running queries running at same time as updates on same table. (not always possible, but think about it: a "long running query" is often a "report" of some sort (not always, but often). Try to schedule the reports when less update activity is expected. Or, if the updates are part of the same batch, try to schedule them after each other so they don't overlap. (if the updates are online users, there isn't much you can do except try to decrease runtime of the long running query).
You DBA can help find candidates for those cases.

ORA-01555 Snapshot too old, rollback segment too small after flashback tab

Hello
Further to an update on a table in database, I realize that I have done an error and I want to come back in the state of table before this operation.
For this I use 'Flashback table' as this command :
flashback table 'table_name' to timestamp to_timestamp('2010-11-08 08:00:00 AM','YYYY-MM-DD HH:MI:SS PM')
and I get this error :
ORA-01555 :Snapshot Too Old rollback segment N° x , "_SYSSMU9$", too small
What I can do to not have this problem ? can I avoid it ?
Please helps .
Regards
Edited by: 794982 on 12 nov. 2010 05:05
Edited by: 794982 on 12 nov. 2010 05:05
Edited by: 794982 on 12 nov. 2010 05:06

To set the undo retention period:
Do one of the following:
• Set UNDO_RETENTION in the initialization parameter file.
UNDO_RETENTION = 1800
• Change UNDO_RETENTION at any time using the ALTER SYSTEM statement:
ALTER SYSTEM SET UNDO_RETENTION = 2400;
The effect of an UNDO_RETENTION parameter change is immediate, but it can only be honored if the current undo tablespace has enough space.
For more reference.
http://download.oracle.com/docs/cd/B19306_01/server.102/b14231/undo.htm

ORA-01555: snapshot too old: rollback segment number 3 with name "_SYSSMU3$

A Materalized view is scheduled to update every 12 hours . When it has tried to update it has thrown the error ...
ORA-12008: error in materialized view refresh path
ORA-01555: snapshot too old: rollback segment number 3 with name "_SYSSMU3$"
too small
ORA-06512: at "SYS.DBMS_SNAPSHOT", line 803
ORA-06512: at "SYS.DBMS_SNAPSHOT", line 860
ORA-06512: at "SYS.DBMS_SNAPSHOT", line 841
ORA-06512: at line 1

Hi,
Can you increase the size of the UNDO Tablespace ?
For more information, you can find on this link below:
http://forums.oracle.com/forums/search.jspa?threadID=&q=ORA-01555&objID=c84&dateRange=all&userID=&numResults=15
Cheers

UNdo error (ora-01555) - Snapshot too old error

Hi,
If undo get filled and if we get a snapshot too old error then what is the solution for this error, plz give step by step solution for this.

You prevent ORA-01555 errors by
1) Setting UNDO_RETENTION equal to or greater than the length of the longest running query/ serializable transaction in the system
2) Ensuring the UNDO tablespace is large enough to accomodate the amount of UNDO generated over that period of time.
You would need to determine things like the length of your longest running query, the amount of UNDO getting generated, etc. and adjust your UNDO_RETENTION and UNDO tablespace accordingly.
Justin

Snapshot too old ORA-01555 from select statement (discoverer)??

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