how to get item_key for HRSSA

Hi
I am trying to create a transaction to apply a leave using API.
How can i retrieve the item_key that needs to be passed in the create_transaction API. Where is the item_key for item_type 'HRSSA' taken from.???

HR_TRANSACTION_API.create_transaction
  (p_validate                     =>    false
  ,p_creator_person_id            => 31422
  ,p_transaction_privilege        => 'PRIVATE'
  ,p_product_code                 => 'PER'
--  ,p_url                          =>  null
  ,p_status                       =>  'W'
 -- ,p_section_display_name          in varchar2 default null
  ,p_function_id                  => 1010344
  ,p_transaction_ref_table        => 'PER_ABSENCE_ATTENDANCES'
  ,p_transaction_ref_id           => l_absence_attendance_id
  ,p_transaction_type             => 'WF'