ConvTek has converted and migrated over 75 large Enterprise-wide VSE application portfolios to z/OS using the mass conversion (one-weekend switchover) approach since 1989. Those projects were in the U.S., Europe and Asia. About half of them were completed as a subcontractor to IBM, and the rest as a main contractor. With all projects, ConvTek provided the consultants, project manager, methodology, and tools.