Hi,
If you get ORA-01555: snapshot too old error when you execute any query, then you have a problem with undo management or undo tablespaces.
This error occurs when your undo_retention parameter is small or undo_tablespace size is insufficient. You need to increase undo_retention parameter like below steps in Oracle 19c. Or you should add datafile to the undo_tablespaces to increate tablespace size.
[oracle@MehmetSalih admin]$ sqlplus / as sysdba SQL*Plus: Release 19.0.0.0.0 - Production on Fri Mar 1 14:06:29 2019 Version 19.2.0.0.0 Copyright (c) 1982, 2018, Oracle. All rights reserved. Connected to: Oracle Database 19c Enterprise Edition Release 19.0.0.0.0 - Production Version 19.2.0.0.0 SQL> show parameter undo NAME TYPE VALUE ------------------------------------ ----------- ------------------------------ temp_undo_enabled boolean FALSE undo_management string AUTO undo_retention integer 900 undo_tablespace string UNDOTBS1 SQL> SQL> SQL> alter system set undo_retention=90000 scope=both; System altered. SQL>
Or Add datafile to Undo tablespace as follows.
If you use ASM Storage then run the following.
ALTER TABLESPACE UNDOTBS01 ADD DATAFILE '+DATA' SIZE 15M AUTOEXTEND ON MAXSIZE UNLIMITED;
If you use File system Storage then run the following.
ALTER TABLESPACE UNDOTBS01 ADD DATAFILE '/oradata/MSDB/undotbs0101.dbf' SIZE 15M AUTOEXTEND ON MAXSIZE UNLIMITED;
Do you want to learn Oracle Database for Beginners, then read the following articles.
https://ittutorial.org/oracle-database-19c-tutorials-for-beginners/