How to update the value of last_ds manually

[hashimoto]

Hello,

I'm searching for the way to  manually update the value of "last_ds", which can be checked
by rrdtool info, leaving the value of "last_update" as it is.

Is there any simple way such as using just one or two commands to do what is described above?
Or is there a need to go through rather complicated procedure like dump & restore?

Thank you
Yuya