ora-01555: snapshot too old: rollback segment number

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/