Environment variable ORACLE_UNQNAME not defined. Please set ORACLE_UNQNAME to database unique name

[oracle@localhost ~]$ emctl status

提示
Environment variable ORACLE_UNQNAME not defined. Please set ORACLE_UNQNAME to database unique name.

处理方法：

$sqlplus /nolog
sql>connect sys/密码 as sysdba
sql>alter user dbsnmp identified by admin (更改dbsnmp密码为admin)
sql>drop role MGMT_USER;
sql>drop user MGMT_VIEW cascade;
SQL>drop user sysman cascade;
sql>drop PUBLIC SYNONYM MGMT_TARGET_BLACKOUTS;
sql>drop public synonym SETEMVIEWUSERCONTEXT;
sql>drop public synonym setemviewusercontext;
exit后运行$emca -deconfig dbcontrol db -repos drop
$emca -deconfig control db -repos create

输入SID、监听端口、SYS密码和SYSMAN密码