Global Mainframe Sales Market Size, Share & Demand Report By System Type (Large-Scale Mainframes, Mid-Range Mainframes, Specialized Mainframes), By Deployment Type (On-Premises, Hybrid, Cloud-Based / MaaS), By Application (Transaction Processing, Data Analytics & AI, ERP & Enterprise Applications, Other Applications), By Industry Vertical (Banking & Financial Services, Government & Public Sector, Healthcare & Life Sciences, Retail & E-commerce, Telecom & IT Services, Manufacturing & Logistics), By Region & Segment Forecasts, 2025–2030