title: Removing user-created datafile from SYSTEM tablespace in Oracle
body: <p>While attempting to create a replacement tablespace for USER, I accidentally created a datafile in SYSTEM</p>
  
  <p>Too many applications are using the database to bring down the entire database, and people will get hurt if these applications are not running.  </p>
  
  <p>Is there a way for me to remove the datafiles from the SYSTEM tablespace without bringing it down?</p>
  
  <p>I tried:</p>
  
  <pre><code>ALTER TABLESPACE SYSTEM DROP DATAFILE 'path_here.dbf'
  </code></pre>
  
  <p>but get this error:</p>
  
  <pre><code>Error starting at line 1 in command:
  alter tablespace system drop datafile 'path_here.dbf'
  Error report:
  SQL Error: ORA-01541: system tablespace cannot be brought offline; shut down if necessary
  01541. 00000 -  "system tablespace cannot be brought offline; shut down if necessary"
  *Cause:    Tried to bring system tablespace offline
  *Action:   Shutdown if necessary to do recovery
  </code></pre>