The ORACLE_SID is the schema ID (instance) of the database that you wish to connect to. You will need to ask somebody what SID you should connect to. Actually, find the oratab file. You should have permissions to view this file. When you find it, open it up. It will have a series of entries with the format like this:
Code:
database_sid:oracle_home_dir:Y|N
Choose which SID you want to connect to based upon entries in this file (still probably want to ask somebody if you are truly not sure of what DB you should be in).
