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I got this error while starting new connection in Oracle 11g:

Listern refused the connection with the follwoing error: ORA-12505,TNS: Listner does not currently know of SID given in connect descriptor the connection descriptor used by the client was: localhost:1521:xe

What is the SID and how can I fix the error?

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Do you have access to the Oracle server or are you doing this from a client? – REW Apr 15 '11 at 21:14

The SID in this case is XE (think of the SID being the database name). The Error means that the listener is not configured to listen for a database called XE on port 1521 on server localhost. Unless you are running the client and server on the same box localhost isn't likely to be correct - change this to the server name. This looks like a connection to Oracle XE which isn't available for 11g (yet) so it isn't clear what your set-up is exactly and so it is difficult to provide a definitive answer - but most likely wither the database is down or you are connecting to the wrong server.

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