How to use Constraint Equations when restarting analysis

[yasaraw]

Hi all,

I try to use constraint equations to connect 2 nodes(actually to give relative displacement) using constraint equations.

This is a transient analysis,which i am restarting the analysis to introduce several load steps.

I can use constraint equations in one load step, and then I try to restart the analysis and program gives a error massage saying "constraint equation 1 does not exist. CECMOD is ignored"

whats the meaning of this?how can I overcome this?even I delete the constraint equation I can not restart it after that.

what can I do?

Thank you