Hi,
Thank you for posting in Symantec community.
Q, Now here is my question, we are running older 12.1.1 SEP Client and will upgrade to the latest client, is it ok to not reboot after uninstalling old sep before installing the latest sep client?
--> Not possible, Operating system needs a reboot.
Why you want to uninstall existing SEP version prior to install latest one? With this approach you need reboot at each workstation prior to install as well.
I would recommend to upgrade the SEP clients over the existing version.
SEP 12.1 employs a side-by-side, replace on reboot installation strategy. Side-by-side means that new files are written to a new folder, referred to as a silo, isolated from the existing operational folder. Because the two versions are separated from each other, during a migration the older software is left running unchanged until the next reboot.
The primary benefit of side-by-side installation and replace on reboot is that the system continues to be protected by the existing software until the new version is in operation after the reboot.