How will you measure Slack for setup and hold time?

Slack setup and hold time are measured following way:

Setup slack = Data required time-data arrival time
Hold slack = data arrival time-data required time

Slack time is defined as the time interval between the actual and desired data to clock time. The data’s transit time through the timing path is referred to as the arrival time. The required time is the length of time needed for the clock to complete one rotation of the clock path.

Which is more dangerous to the design specifications and working mode, setup time violation and hold time violation?

The setup time violation depends on the frequency. It can be eliminated or minimized by adjusting the clock’s frequency. In comparison, a hold time violation is a design functional failure. It doesn’t depend on frequency. Slowing down the clock’s frequency won’t help because it will cause data racing. Consequently, the design with the setup time violation can be employed with a different clock period, but the design still has the hold time violation.