如果静态监听中ORACLE_SID不注意大小写的话，可能导致数据库连接不上的问题。如下案例所示:
$ sqlplus system/***@GPSUAT
SQL*Plus: Release 19.0.0.0.0 - Production on Wed Sep 18 15:48:37 2024
Version 19.24.0.0.0
Copyright (c) 1982, 2024, Oracle. All rights reserved.
ERROR:
ORA-01034: ORACLE not available
ORA-27101: shared memory realm does not exist
Linux-x86_64 Error: 2: No such file or directory
Additional information: 4480
Additional information: -1989017509
Process ID: 0
Session ID: 0 Serial number: 0
Enter user-name:
ERROR:
ORA-01017: invalid username/password; logon denied
检查数据库实例正常。使用tnsping检查服务的网络是否正常，如下所示：
$ tnsping GPSUAT
TNS Ping Utility for Linux: Version 19.0.0.0.0 - Production on 07-NOV-2023 08:35:42
Copyright (c) 1997, 2022, Oracle. All rights reserved.
Used parameter files:
Used TNSNAMES adapter to resolve the alias
Attempting to contact (DESCRIPTION = (ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.9.40)(PORT = 15021)) (CONNECT_DATA = (SERVER = DEDICATED) (SERVICE_NAME = GPSUAT)))
OK (10 msec)
数据库中tnsnames.ora的配置如下所示：
GPSUAT =
(DESCRIPTION =
(ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.9.40)(PORT = 15021))
(CONNECT_DATA =
(SERVER = DEDICATED)
(SERVICE_NAME = GPSUAT)
)
)
此时，监听的配置如下
$ more listener.ora
GPS =
(DESCRIPTION_LIST =
(DESCRIPTION =
(ADDRESS = (PROTOCOL = IPC)(KEY = GPS))
(ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.9.40)(PORT = 15021))
(ADDRESS = (PROTOCOL = TCPS)(HOST =192.168.9.40)(PORT = 15022))
)
)
SID_LIST_GPS =
(SID_LIST =
(SID_DESC =
(SID_NAME = GPS)
(ORACLE_HOME=/opt/oracle19c/product/19.3.0/db_1)
)
(SID_DESC =
(GLOBAL_DBNAME = GPSUAT)
(SID_NAME = GPS)
(ORACLE_HOME=/opt/oracle19c/product/19.3.0/db_1)
)
(SID_DESC =
(GLOBAL_DBNAME = GPSUAT2)
(SID_NAME = GPS)
(ORACLE_HOME=/opt/oracle19c/product/19.3.0/db_1)
)
)
SECURE_REGISTER_GPS = (IPC)
SECURE_CONTROL_GPS =(TCPS,IPC)
ADMIN_RESTRICTIONS_GPS = ON
DIAG_ADR_ENABLED_GPS = OFF
正确的配置如下（SID_NAME必须使用小写，跟实例的大小写一致。这里ORACLE_SID值为gps）
$ more listener.ora
GPS =
(DESCRIPTION_LIST =
(DESCRIPTION =
(ADDRESS = (PROTOCOL = IPC)(KEY = GPS))
(ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.9.40)(PORT = 15021))
(ADDRESS = (PROTOCOL = TCPS)(HOST =192.168.9.40)(PORT = 15022))
)
)
SID_LIST_GPS =
(SID_LIST =
(SID_DESC =
(SID_NAME = gps)
(ORACLE_HOME=/opt/oracle19c/product/19.3.0/db_1)
)
(SID_DESC =
(GLOBAL_DBNAME = GPSUAT)
(SID_NAME = gps)
(ORACLE_HOME=/opt/oracle19c/product/19.3.0/db_1)
)
(SID_DESC =
(GLOBAL_DBNAME = GPSUAT2)
(SID_NAME = gps)
(ORACLE_HOME=/opt/oracle19c/product/19.3.0/db_1)
)
)
SECURE_REGISTER_GPS = (IPC)
SECURE_CONTROL_GPS =(TCPS,IPC)
ADMIN_RESTRICTIONS_GPS = ON
其实secooler的这篇博客配置静态监听时谨防SID_NAME大小写问题导致数据库无法连接[1]中已经对这个问题进行了详细的描述，这里不做重复展开讨论了，直接应用它的结论。如下所示：
在监听静态注册的环境中，listener.ora文件中写的实例名，要区分大小写，否则虽然远程telnet 监听端口是通的，但依旧会报出数据库不可用的问题。
之所以会报出数据库不可用问题，是由于远程连接通过监听连到的是另外一个库，而该库没有启动或者不存在。
总结：以后在处理问题中，注意区分实例名大小写问题，在监听层面，动态监听和静态监听很容易混淆实例名问题，尤其当服务器上存在大小写不同的数据库时候。
1: http://blog.itpub.net/519536/viewspace-704704/
原文始发于微信公众号（DBA闲思杂想录）：Oracle静态监听中SID_NAME区分大小写吗？
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