Oracle - ORA-01034: ORACLE not available Process ID: 0 / Connected to an idle instance

一、異常

[oracle@xl ~]$ sqlplus / as sysdba

SQL*Plus: Release 11.2.0.1.0 - Production on Mon Jun 4 00:55:19 2017

Copyright (c) 1982, 2009, Oracle. All rights reserved.

Connected to an idle instance.

-- 後面再做其他操作時拋的異常
SQL> select instance_name from v$instance; 

ERROR at line 1:
ORA-01034: ORACLE not available
Process ID: 0
Session ID: 0 Serial number: 0

二、原因

    1、遇到過一種情況是伺服器的記憶體爆了
    2、網上也有說是伺服器ORACLE_SID環境變數與資料庫的instance_name例項名不一致的