Below Image clearly shows when we need to use SUM 2.0 or SUM 1.0
SUM 1.0 and 2.0 are offered in parallel. But each scenario is covered by only one of the SUM versions – the other SUM version will refuse to work on that scenario
Easy decision matrix:
* SUM 2.0 is for ABAP single stacks, targeting systems based on BASIS 7.50 and higher
(exception: SUM 2.0 is used for ZDO even if target is BASIS 7.40)
* SUM 1.0 is always used if the source system is either a dual-stack system, or a Java stack
* SUM 1.0 is used for ABAP stack if target is based on BASIS 7.40 or lower
(exception: SUM 1.0 is used for upgrade of SAP Process Integration (SAP PI) dual stack systems to SAP PI NetWeaver 7.50, read more in the Upgrade Master Guide )
The consequences:
all System Conversions (transition SAP ERP to SAP S/4HANA) will be done by SUM 2.0.
SUM 2.0 targets BASIS 7.50 and higher, which in turn requires that
the source system is already Unicode, and
the source is based on BASIS 7.00 or higher
Note:
Also when you planning for upgrade SAP system, during the process we generate XML file through maintenance planner, and during that
maintenance planner pick the correct version of SUM, either SUM 1.0 or SUM 2.0 ( depends on our system product version).
And its important that, we do read SUM latest SUM version guide that we are planning to use.