Upgrade wasn't completed Severe error(s) occured in phase PREP_INIT/VALCHK_INI!

The message appears on upgrade:

Last error code set: PI_BASIS is in an undefined state, that is not safeto be upgraded, reason Upgrade wasn't completed - Call the SAP Support

Solution:

Truncate the table UVERS

Run the transaction $tab to reset buffer tables in SAP

Restart Upgrade