title: SQLDeveloper - Listener refused the connection with the following error: ORA-12505
body: <p>I just got started with Oracle, so I don't know anything about it.</p>
  
  <p>I just installed oracle 11g, and used SID: orcl1. After unlocking hr user and giving it a password I downloaded SQLDeveloper and tried to create a connexion with the hr user using SID: orcl1 and it's password.</p>
  
  <p>It gives me the following Error:
  SQLDeveloper - Listener refused the connection with the following error: ORA-12505. TNS:listener does not currently know of SID given in connect descriptor</p>
  
  <p>I searched it and seems to be a problem with SID, but I couldn't find a solution and as I'm totally new at this, I don't understand most of the posts. Could anyone help me please?</p>
  
  <p>Thanks.</p>
  
  <p>Pd: I don't know why do I have to make this connection but the instructor of the course I'm following says it's important.</p>