set serveroutput on;
declare
v_sql varchar2(80);
v_pdb varchar2(30);
BEGIN
  FOR pdb IN (select name from v$pdbs where con_id=3 and OPEN_MODE='READ WRITE')
  LOOP
    v_sql := 'alter session set container='||pdb.name||';';
    DBMS_OUTPUT.PUT_LINE('Executing: ' || v_sql);
    execute immediate 'alter session set container='||pdb.name||';';
    execute immediate 'show con_name';
    execute immediate 'drop user bigschema cascade';
 END LOOP;
END;
/