Installed Base update using csi_item_instance_pub.update_item_instance in 11i, not reflecting on chi

Hi,

I m using csi_item_instance_pub.update_item_instance for updating Installed_date on the Parent Instance.

When I update on the parent instance , it is getting updated only on the parent instance and it is not flowing down to child instance.

Could you let me know why the update is not flowing to child.

148192802  => Parent

   148192801  => child

       148192806 => child

l_instance_rec_rm.install_date          := '25-JUN-2015';

Thanks