Whenever possible and desirable, ConvTek recommends using the mass conversion approach, which consists in fully automating the conversion process, so that the entire application inventory can be simultaneously migrated from source to target environments over a few hours with minimum end-user service disruption and minimum end-user visibility. 

The mass conversion approach is the preferred approach for transformation projects in which several types of applications items (JCL streams, data files, programs, etc) are impacted and must be simultaneously modified in order for the application to remain functional. The mass conversion is almost unavoidable when applications are highly integrated through shared databases and permanent files, or through shared production tools like a job scheduler or report manager. The mass conversion is therefore the preferred approach for:

• VSE to z/OS migration
  
• Field expansion
  
• MVS JCL reengineering
  
• Non-IBM to IBM migration
  
• DB2 migration

The mass conversion approach is not justified for transformation projects that can be implemented one program at a time, and for which conversion grouping is only required to facilitate regression testing. A progressive conversion is the appropriate approach for:

• SAS to COBOL conversion
  
• Language conversion
  
• COBOL transformation