Hello Ibrahim,
as far as I remember it is specific to each SMU.
There are SMU that can be installed without a reboot. There are other SMUs that require reload.
Also the order of installation of multiple SMUs is important.
This information should be reported in the download SW center where you download the SMUs. There should be a brief text description and a note about the need or not of a reload after installation.
To make an example I had to install 30 SMUs on a CRS-1 device and it required four different reloads during the process.
It took hours to complete and we had to use a maintenance window.
Hope to help
Giuseppe
