ORA-01033 ORACLE正在初始化或关闭

SQL Developer连接oracle12c时，报错：“ORA-01033 ORACLE正在初始化或关闭”

原因：oracle 12c的PDB数据库未打开
解决方案：进入cmd

-- 连接
sqlplus / as sysdba
-- 查看PDB数据状态
select con_id,name,open_mode from v$pdbs;
alter pluggable database ORCLPDB open;
alter session set container=ORCLPDB;
commit;