nomount 时 :
实例状态:select status from v$instance; STARTED
数据库状态:select open_mode from v$database; ERROR at line 1: ORA-01507: database not mounted
mount 时:
实例状态:select status from v$instance; MOUNTED
数据库状态:select open_mode from v$database; MOUNTED
open 时:
实例状态:select status from v$instance; OPEN
数据库状态:select open_mode from v$database; READ WRITE 或者 READ ONLY