Interesting.
Although forcing a resync would be the ideal situation, I doubt DLM is clever enough to detect that the low SNRM could be an effect of resyncing before crosstalkers.
It is indeed interesting. It wouldn't take much for DLM to identify that a simple resync is enough - it just needs to check whether the recent actual SNRM is significantly below the defined target SNRM (be it 6, 5, 4 or 3dB). But ... I don't think DLM has historically collected the SNRM data to be able to make that decision from.
If DLM decides that some action is necessary, then the logical process would be to reverse the target SNRm steps.
Actually whilst typing this, I just recalled that I think that may have been what it did on Williams line.
As banger has subsequently replied, his line does indeed seem to reverse that final step - and does so quite nicely. I have been relieved to see that it seems to take this reversal step within its stride.
I imagine, therefore, that DLM has to now try to keep a green/amber/red status for each of the possible target SNRM values, so it can identify what to step back to, and for human-based (engineering centre of excellence?) intervention.
William's line was the first (visible) line that got the XdB treatment during the trial, and followed a pattern of 6-5-4-3-6. At the time, I wondered whether the step back to 6dB was a poor "undo" function, or if it was a deliberate pre-stage to see what the line was capable of at each target, rather than proper live functionality.