Either do a find on your computer for your tnsnames.ora file, or go to your oracle directory
mine is in
c:\oracle\ora81\network\admin
Open this file in a text editor. Find your entry for this database that you use to connect to, and the first part is the sid name.
DATA_SID =
(DESCRIPTION =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = TCP)(HOST = database.blah.com)(PORT = 1521))
)
(CONNECT_DATA =
(SERVICE_NAME = myServiceName)
)
)
DATA_SID would be the sid in the above example from the tnsnames.ora file.
I don't mean to be rude in the following statement, so please don't take it that way. If you don't know what a sid is, you might want to ask your DBA. If you don't have a DBA, who is managing your Oracle server? go to that person.
Mark