Note:
1. We are running a single node RAC on Red Hat 5 Update 3
2. We are running 11.2.0.1 of the database

[oracle@jin1 ~]$ . oraenv
ORACLE_SID = [dbtools1] ? +ASM1
The Oracle base for ORACLE_HOME=/apps/11.2.0/grid is /apps/oracle
[oracle@jin1 ~]$ srvctl start database -d DBTOOLS
[oracle@jin1 ~]$ . oraenv
ORACLE_SID = [+ASM1] ? DBTOOLS1
The Oracle base for ORACLE_HOME=/apps/oracle/product/11.2.0/dbhome_1 is /apps/oracle
[oracle@jin1 ~]$ emctl start dbconsole
Environment variable ORACLE_UNQNAME not defined. Please set ORACLE_UNQNAME to database unique name.

Interestingly new, you have to set the ORACLE_UNQNAME environment variable to start dbconsole.

[oracle@jin1 ~]$ export ORACLE_UNQNAME=DBTOOLS
[oracle@jin1 ~]$ emctl start dbconsole
Oracle Enterprise Manager 11g Database Control Release 11.2.0.1.0
Copyright (c) 1996, 2009 Oracle Corporation.  All rights reserved.

https://jin1.dbaexpert.com:1158/em/console/aboutApplication

Starting Oracle Enterprise Manager 11g Database Control ............... started.
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Logs are generated in directory /apps/oracle/product/11.2.0/dbhome_1/jin1_DBTOOLS/sysman/log

Posted by Charles Kim, Oracle ACE