Oracle Entreprise Manager is a monitoring tool which provides all the information you need about the existing instances, their datafiles, the sessions and much more.
To check whether it is running or not :
oracle@localhost:~$ ps -ef |grep dbconsole |grep -v grep
oracle 31842 1 0 10:31 ? 00:00:00 /opt/oracle/oracle/product/10.2.0/db_1/perl/bin/perl /opt/oracle/oracle/product/10.2.0/db_1/bin/emwd.pl dbconsole /opt/oracle/oracle/product/10.2.0/db_1/$HOSTNAME_$ORACLE_SID/sysman/log/emdb.nohup
To stop it :
oracle@localhost~$ emctl stop dbconsole
To start it :
oracle@localhost:~$ emctl start dbconsole
To check its status :
oracle@localhost:~$ emctl status dbconsole
emctl status dbconsole
TZ set to Europe/London
Oracle Enterprise Manager 10g Database Control Release 10.2.0.4.0
Copyright (c) 1996, 2007 Oracle Corporation. All rights reserved.
Oracle Enterprise Manager 10g is running.
Logs are generated in directory /opt/oracle/oracle/product/10.2.0/db_1/$HOSTNAME_$ORACLE_SID/sysman/log
$ORACLE_SID : contains the value of the Oracle SID.
$HOSTNAME : contains the hostname of the server on which Oracle Entreprise Manager is running.
To use emctl directly, make sure that your $PATH contains the path to Oracle binaries. You can find most of them in $ORACLE_HOME/bin