Make changes in PDB$SEED when it's in Read only.

 

When a PDB$SEED in in read only mode it doesn't allow us to run any alter/DDL/DML statements. In this case setting a hidden parameter allows us to run them.

•  Connect to PDB$SEED.

sqlplus / as sysdba
ALTER SESSION SET CONTAINER = PDB$SEED;

• Verify that you are in PDB$SEED

show con_name (or) show pdbs

• Set the hidden parameter

alter session set "_oracle_script" = true;

• Close the PDB and open it in read wirte mode.

alter pluggable database pdb$seed close;
alter pluggable database pdb$seed open read write;

• After required changes are done (alter,update,delete,insert) put the database back in read only. 

alter pluggable databsae pdb$seed close;
alter pluggable database pdb$seed OPEN READ ONLY;

• Disable the hidden parameter.

alter session set "_oracle_script"=FALSE;