In the paper, we develop further the properties of Schur rings over infinite groups, with particular emphasis on the virtually cyclic group Z × Zp. We provide structure theorems for primitive sets in these Schur rings.In the case of Fermat and safe primes, a complete classification theorem is proven which states that all Schur rings over Z × Zp are traditional. We also draw analogs between Schur rings over Z × Zp and partitions of difference sets over Zp.