One investigation stems from complaints by emulator software vendors T3 and Turbo Hercules, which accuse IBM of tying the sale of mainframe hardware to its mainframe operating system, the European Commission said.
The other, begun at the EU executive's own initiative, accuses IBM of "discriminatory behavior toward competing suppliers of mainframe maintenance services."
The opening of EU antitrust investigations does not mean the European Commission has proof of any wrongdoing, only that it sees cause for a deeper look into corporate behavior.
The European Commission said T3 and Turbo Hercules complain that IBM, by tying its hardware and operating systems together, "shuts out providers of emulation technology which could enable the users to run critical applications on non-IBM hardware."
Its own complaint addresses the concern that IBM "may have engaged in anticompetitive practices" by keeping competitors in maintenance services at bay, "by restricting or delaying access to spare parts for which IBM is the only source."
Mainframes are powerful computers used by large corporations and governments to store and process critical business information. It is estimated the vast majority of corporate data worldwide resides on mainframes.
The European Commission estimated worldwide sales of mainframe computers and operating systems in 2009 at euro8.5 billion. It put sales in Europe at about euro3 billion that year.
T3 and Turbo Hercules make "emulators" software that acts as if it is running on an IBM mainframe whereas it is actually running on cheaper servers.