Oracle DB - linux based ORACLE_SID 大小寫區分 case sensitivity

[root@testdb88 build]# su - oracle
[oracle@testdb88 ~]$ env|grep ORA
ORACLE_UNQNAME=DB11G
ORACLE_SID=DB11G
ORACLE_BASE=/u01/app/oracle
ORACLE_HOSTNAME=testdb88
ORACLE_HOME=/u01/app/oracle/product/11.2.0/db_1
[oracle@testdb88 ~]$ export ORACLE_SID=db11g
[oracle@testdb88 ~]$ env|grep ORA
ORACLE_UNQNAME=DB11G
ORACLE_SID=db11g
ORACLE_BASE=/u01/app/oracle
ORACLE_HOSTNAME=testdb88
ORACLE_HOME=/u01/app/oracle/product/11.2.0/db_1
[oracle@testdb88 ~]$ sqlplus / as sysdba

SQL*Plus: Release 11.2.0.4.0 Production on Fri Nov 15 13:05:01 2019

Copyright (c) 1982, 2013, Oracle.  All rights reserved.

Connected to an idle instance.

SQL> exit
Disconnected
[oracle@testdb88 ~]$ export ORACLE_SID=DB11G
[oracle@testdb88 ~]$ sqlplus / as sysdba

SQL*Plus: Release 11.2.0.4.0 Production on Fri Nov 15 13:05:26 2019

Copyright (c) 1982, 2013, Oracle.  All rights reserved.


Connected to:
Oracle Database 11g Release 11.2.0.4.0 - 64bit Production

SQL> exit
Disconnected from Oracle Database 11g Release 11.2.0.4.0 - 64bit Production