1. An operating method of a memory system comprising: performing a symmetric Oversampling (OVS) read with at least an initial read threshold, and creating a symmetric read result; performing an asymmetric OVS read with at least the initial read threshold, and creating an asymmetric read result; adjusting the initial read threshold according to at least the symmetric read result and asymmetric read result, and creating an optimal read threshold; and executing data recovery process with the optimal read threshold.