text: **Note:**You can update the application group to add a database field. 
  
  When you define a field, you specify the field name, field type, data type, whether it is a 
  segment field, the expiration date, and more. In the following sections, we take a closer look 
  at field type and whether it is a segment or an application ID field. 
  
  **Type**
  The Type attribute determines the manner in which the database field is used by Content 
  Manager OnDemand. The main types of attributes are*index*and*filter*. 
  
  A field needs a type of*index*if it is used to uniquely identify a document or if it is frequently 
  used when a user searches for documents in the application group. Designating a field as an 
  index serves to enhance query performance but increases the required processing during 
  loading and database maintenance. A separate index table is created and maintained for 
  application group fields that are designated as indexes. These index tables are searched first 
  when a*folder*query is run to quickly pinpoint the documents to include in the document “hit” 
  list. 
  
  A field needs a type of*filter*if it does not uniquely identify a document. A filter is used with an 
  index field during folder queries. 