title: Oracle drop column from compressed table - behind the scenes "set unused"
body: <p>Working with Oracle 11.2.0.4.0 and trying to drop columns from several OLTP compressed tables, was expecting to get <code>ORA-39726:  unsupported add/drop column operation on compressed tables</code>. However, it has <strong>run without error but leaving the columns unused</strong>. </p>
  
  <p>I was wondering if this behavior could be avoided - I'd like to get the error, in order to avoid confusion (people leaving unused columns all over the place without knowing so).</p>
  
  <p>I could not find references to this, need to boost my searching skills. In the documentation I see only:</p>
  
  <blockquote>
    <p>You can set unused a column from a table that uses COMPRESS BASIC, but
    you cannot drop the column. However, all clauses of the
    drop_column_clause are valid for tables that use COMPRESS FOR OLTP.
    See the semantics for table_compression for more information.
    <a href="http://docs.oracle.com/cd/E11882_01/server.112/e41084/statements_3001.htm#i2103683" rel="nofollow noreferrer">http://docs.oracle.com/cd/E11882_01/server.112/e41084/statements_3001.htm#i2103683</a></p>
  </blockquote>
  
  <p>Please do you know any way to configure it to raise the error?
  The scenario:</p>
  
  <pre><code>create table test_radu_a(col1 number, col2 number) compress for oltp;
  alter table test_radu_a drop (col2);
  select * from user_unused_col_tabs where table_name = 'TEST_RADU_A';
  </code></pre>