Make sure all the necessary environment variables are set, especially the following variables.

  1. ORACLE_SID
  2. ORACLE_HOME
And follow the below steps to start, database, listener and enterprise manager(em) console
  • For db startup: 

             oracle@root.com$ sqlplus / as sysdba
SQL*Plus: Release 11.1.0.6.0 – Production on Sun Nov 9 22:52:26 2008
Copyright (c) 1982, 2007, Oracle. All rights reserved.
Connected to an idle instance.

SQL> startup;
ORACLE instance started.
Total System Global Area 1389391872 bytes
Fixed Size 1299848 bytes
Variable Size 838863480 bytes
Database Buffers 536870912 bytes
Redo Buffers 12357632 bytes
Database mounted.
Database opened.

SQL> exit
Disconnected from Oracle Database 11g Enterprise Edition Release 11.1.0.6.0 – Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options

  • Starting listener
              oracle@root.com$ lsnrctl start
  • Oracle Enterprise manager start
              oracle@root.com$  emctl start dbconsole
Now the enterprise manager server is started and can be accessed using the link on browser : https://hostname:1158/em
Thank u 🙂