Hi Fue,
If these devices are in DNS, then you can change the "Naming Order" for the VNM to use DNS instead of SysName. This change is global and will impact all device models for that VNM.
If you locate the VNM model (looks like an orange lower-case I) and go to the Component Detail pane - Information Tab in OneClick. Once there, expand the SpectroSERVER Control subview, you should find "Model Naming Order" settings. This controls the order of the protocols Spectrum uses when determining a device models name. The order is read from top down. By default the order is SysName, IP Address, Name Service.
If you make a change to the order, you will want to have Spectrum re-evaluate the model names to update the models with the DNS names. For more information see TEC158764 "How to Configure Spectrum to Name the Device Models Using the Host Name and Not the Fully Qualified Host Name" (https://support.ca.com/us/knowledge-base-articles.TEC518764.html).
If the devices in question aren't in DNS, then you can manually change the Model Name (Model_Name attr 0x10031) and then lock the model name by setting the Lock_Model_Name attribute 0x12a52 to "yes". This will keep Spectrum from changing the model name back to the sysName at the next poll interval.
Hope this helps,
Brad