...

When running S2PX translated PX jobs it failed with the error message APT_CombineOperatorController,0: FatalError: Null value on the accessor interfacing to field "column".

...

Cause

DataStage older than 11.7.1.4 SP1 has problem handling derivation likeof the form …

If StrCmp(DSLink.column, "@") = 0 Then
  SetNull()
Else
  DSLink.column[2, Len(DSLink.column)-1]

Solution

Update your DataStage platform to v11.7.1.4 SP1 or abovelater.