An identity search is similar in function to an identity map, except that an identity search actually searches the directory for the user DN rather than reconstructing it from the simple username.
If you configure one or more identity searches, the directory automatically performs a service bind when a user logs on. The service bind is automatic, so you do not need to set the LdapServiceBindRequired property, but you must configure other properties related to service binds. See Working with Service Binds.