title: how to avoid reaching max size of varchar2 in concat with update
body: <p>I am new to oracle. when updating a table i am using </p>
  
  <pre><code>update my_table set column_name =concat(" ' ", column_name, "viewed by xxxx") 
  where item_value=2. 
  </code></pre>
  
  <p>this value is being appended whenever some one is viewing...
     Now my question is  How to avoid max size of varchar(2) and set if it is just 50 characters lesser than its size. I am using this in servlet </p>
  
  <p>My requirement is ..If some user views the item_value of 2, his userid is to be entered in my_table by concatinating the existing values in column_name where item_value=2, in one word I dont want to loose the earlier data in field when updating and to avoid reaching the max size of the field which is varchar2(900).  </p>
  
  <p>If the field reaches max size then the existing data will be ovewritten by the new data else it will be a concatination to existing data.</p>