Engg. change mgmt doubt

Hi PP Experts,

Please explain the below ECM query.

I have one lead change master with 1 MCO.Now i closeded the lead change master, without closing the MCO attached to this.

And not able to change any status in MCO  from 70.

Is that mandatory to closer the MCO first before closing the LCM. Please explain.

Thanks in advance.

BR,

Suresh.