Which databases are running on the machine
From dbawiki
From Unix
ps -ef|grep [o]ra_smon|sed -e 's/.*_//'|sort|uniq
From Windows
services.msc
Look through list for services beginning with OracleService<SID>
How to see what databases have been defined (running or not)
cat /var/opt/oracle/oratab (Solaris)
cat /etc/oratab (others)
