title: Oracle Database12c ORA 01918 and connection error
body: <p>I have installed the Oracle 12c and I have  problems creating my first database and using it.
  I run SQL Developer and use "hr" user but it keeps telling me that the account is locked. I searched into stackoverflow answers and official doc and tried to unlock it with:</p>
  
  <pre><code>ALTER USER HR IDENTIFIED BY password ACCOUNT UNLOCK;
  </code></pre>
  
  <p>but with no success. I got error ORA01918, meaning that user does not exist. </p>
  
  <p>I tried then to use the user created at the installation (SYS as SYSDBA)but then it says that the user/password is incorrect. I am pretty sure that I have installed Oracle 12c correctly on my system, which is Windows 8.1 x64.</p>
  
  <p>What should I do? Please help me. </p>
  
  <p>Other thing I do not understand is wether or not the term "database" is equivalent to MySQL's "Schema"? The "connection" is to connect to a specific database, yes?
  Thank you.</p>