Deployment Enginee is the installer that installs new Tivoli Netcool products, eg, OMNIBus 7.3 , ITNM 3.8 and others.
in older version changing hostname after Netcool application has been installed is not a big deal, admin need to change some application related files and things will be alright.
with those DE enabled product there is one more thing to change.
if the product was installed use root user, admin will need to edit /var/ibm/common/acsi/ACUApplication.properties, change acu.hostname to the changed hostname.
if the product was installed as normal user, eg, netcool, you can find this file in that user's home directory.
you have the choice of not changing this file, the application will run perfectly fine, but you will not be able to install new product or apply patch on top of it.