title: Why is it impossible to drop user despite it exists in dba_users view
body: <p>I try to drop/alter user like this</p>
  
  <pre><code>drop user AVASILIEV_AXIOM_10X
  </code></pre>
  
  <p>And I get the following error</p>
  
  <pre><code>SQL&gt; drop user AVASILIEV_AXIOM_10X;
  drop user AVASILIEV_AXIOM_10X
            *
  ERROR at line 1:
  ORA-01918: user 'AVASILIEV_AXIOM_10X' does not exist
  </code></pre>
  
  <p>But this user exists in the dba_users view:</p>
  
  <pre><code>SQL&gt; select username from dba_users where username='AVASILIEV_AXIOM_10X';
  
  USERNAME
  ------------------------------
  AVASILIEV_AXIOM_10X
  
  SQL&gt;
  </code></pre>
  
  <p>Also, I can't create user with the same name because it already exists in the DB. What's the problem?</p>
  
  <p>My Oracle version:
  Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit Production
  PL/SQL Release 11.2.0.4.0 - Production
  "CORE   11.2.0.4.0  Production"
  TNS for Linux: Version 11.2.0.4.0 - Production
  NLSRTL Version 11.2.0.4.0 - Production</p>