I'm not a SAS Grid expert but I've been working in such environments. You don't need to change your code and you still will connect to a single server in SAS metadata.
Yes, in the background there are now multiple compute servers (grid nodes) to which processing will be distributed but that's something the SAS Grid Manager will handle for you in the background. It's nothing you have to care about.
You mention Putty. As there are now multiple compute servers you're going to connect to one of them (one of the nodes). If you're issuing SAS code via command line in batch then just use sas.sh to pass in your parameters, i.e: nohup .../Config/Lev1/SASApp/sas.sh -sysin <your SAS program> &
sas.sh will set all the environment specific configuration required to run your code in your environment.
http://support.sas.com/documentation/cdl/en/gridref/67371/HTML/default/viewer.htm#n049jf2x471mybn1pn9f6tpz3400.htm
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