What is the ruling for someone who remembers a missed Dhuhr prayer while performing Asr, whether individually or in congregation?

Scholars differ concerning one who remembers a missed prayer while performing a present prayer. The preponderant opinion is that he should complete the present prayer, then make up the missed one. It is also recommended to repeat the present prayer, because orderly sequence is not obligatory. This ruling applies equally to both the Imam and the congregant.