The sylink.xml file is used by the Symantec Endpoint Management Client (smc.exe) to work out which management server to use. If you want to change the management server over to a new one you can replace the existing sylink.xml file with a new one and then restart smc.exe on the client.
The file is located
C:\Documents and Settings\All Users\Application data\Symantec\Symantec Endpoint Protection\LATESTVER\Data\Config
C:\ProgramData\Symantec\Symantec Endpoint Protection\LATESTVER\Data\Config