Cause
This error occurs under the following conditions.
If a server method attempts to exclusively lock a persistent object while in transaction state, and the object is already locked by a method executing on the client node.
If a client method attempts to exclusively lock a persistent object while in transaction state, and the object is already locked by a server method request.
If a server method attempts to lock a persistent object when the object is exclusively locked by a method executing on the client node and transaction state is in effect on the client node.
If a client method attempts to lock a persistent object when the object is exclusively locked by a server method request and transaction state is in effect on the server node.
Action
Change your application code to ensure that the requested object is not already locked when calling a remote method that updates it, or so that the method is not accessing an object that has been updated but not committed on the other node.