Start two SUM tools simultaneously (in the same server with different OS users)

Hello,

I need to perform two SAP upgrades using the SUM tool, in a server that have two SAP instances installed.

Can I do that? Because when I start the SUM tool with a specific user I went in the same server with other user and when I tried to start the SUM tool using the STARTUP.BAT it give me an error that saying that port is using by the other SUM tool.

It´s possible to do that!? I read the SUM guide but I can´t find any explanation for this!

Can you help me please? What I need to do to start the second SUM tool (for the second upgrade in the same server)?

Thank you,

JD