thank Justin, Errors occurs during the month but we have a very bad application that generate sql scripts with a lot of cursors opened on thoses big tables ( more than 20Go per tables) thoses script create small tables (10 - 200 Mo) with datas pick up from the different big tables. The problem is that the generated script are often launch in the same time and I we can't touch the code. ____________________________________________________ Philippe Nguyen CETELEM - Administration, Architecture Décisionnelle Direction Customer Relationship Management E-Mail : philippe.nguyen@xxxxxxxxxx Tel : (+33) 1 46 39 92 16 - Fax : (+33) 1 46 39 59 88 -----Message d'origine----- De : oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx]De la part de Justin Cave Envoyé : vendredi 11 juin 2004 12:15 À : oracle-l@xxxxxxxxxxxxx Objet : RE: Tbs READ ONLY and Snapshot too old ORA-01555 indicates that Oracle was attempting to reconstruct the state of a block and the earlier state was not available in the undo segments. By definition, you cannot get an ORA-01555 error when trying to access a read-only object. Do you get these ORA-01555 errors shortly after doing the load or do you get them throughout the day? The only thing I can think is that these errors are caused by delayed block cleanout, but that should take care of itself soon after the load. If you get errors throughout the month, I would suspect that the big tables aren't the cause. Justin Cave Distributed Database Consulting, Inc. http://www.ddbcinc.com <http://www.ddbcinc.com/askDDBC> /askDDBC _____ From: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx] On Behalf Of NGUYEN Philippe (Cetelem) Sent: Friday, June 11, 2004 4:15 AM To: oracle-l@xxxxxxxxxxxxx Subject: Tbs READ ONLY and Snapshot too old Hi List, just a little question about read only tbs : We have big tables that are loaded once and never updated during the month , so I think it's a good thing to switch their tbs to read only mode. Web have a lot of script that request thoses heavy tables to build small tables and we often encounter ORA-01555. Do you think that "in general" this operation could enhance our ORA-01555 problems ? TIA Philippe