User & has locked COKL record &

What causes this issue?

DEFINE &USER& = &V1&
INCLUDE MESSAGE_ENQUEUE_USER OBJECT DOKU ID TX
The activity type is currently locked by another user.
An exclusive lock is set when the cost element is being planned.

System Response

Processing is terminated.

How to fix this error?

Contact user &V1& or wait until he or she has finished processing.
You can then proceed with your processing.

Error message extract from SAP system. Copyright SAP SE.