UNDO tablespace size has to be at least 200MB

Click the OK button to dismiss the error and resize the data file associated with the undo table space to 200MB or more.

SQL> select file_name from dba_data_files;
FILE_NAME
---------------------------------------------------
/u02/app/oracle/oradata/gcrepo/users01.dbf
/u02/app/oracle/oradata/gcrepo/undotbs01.dbf
/u02/app/oracle/oradata/gcrepo/sysaux01.dbf

SQL> alter database datafile '/u02/app/oracle/oradata/gcrepo/undotbs01.dbf' resize 400M;
Database altered.