title: not null enable novalidate issue in oracle
body: <p>I have a data existing in my table table_abc.</p>
  
  <p>There is a column context_name which is non-mandatory but now I am trying to modify this column and make it mandaroty</p>
  
  <p>for example :</p>
  
  <pre><code>ALTER TABLE table_abc MODIFY CONTEXT_NAME VARCHAR2(240) NOT NULL;
  </code></pre>
  
  <p>This will throw an error </p>
  
  <p>ERROR at line 1:
  ORA-02296: cannot enable (APPS.) - null values found</p>
  
  <p>So i used novalidate like </p>
  
  <pre><code>Alter table table_abc modify CONTEXT_NAME not null enable novalidate;
  </code></pre>
  
  <p>But now when i am seeing the structure of the table it is not showing context_ame as not null;</p>
  
  <pre><code>Name                  Null     Type           
  --------------------- -------- -------------- 
  NAME                  NOT NULL VARCHAR2(700)  
  ITEM_DESCRIPTION               VARCHAR2(2000) 
  
  ITEM_TEXT_TL_15                VARCHAR2(4000) 
  ITEM_DESCRLONG                 VARCHAR2(4000)     
  CREATED_BY                     VARCHAR2(64)   
  CREATION_DATE                  DATE           
  LAST_UPDATE_DATE               DATE           
  LAST_UPDATED_BY                VARCHAR2(64)   
  LAST_UPDATE_LOGIN              VARCHAR2(32)   
  CONTEXT_NAME                   VARCHAR2(240)   
  BF_NAME          VARCHAR2(264) 
  </code></pre>
  
  <p>Shouldnt context_name be not null ?</p>