After the calculation algorithm has been expanded and before the algorithm is executed the source features (regular features and calculated features) are locked.

The type of lock(s) applied to the source features depends on the actual calculation types used. All source features will be locked against observation modification and observation deletion. If the calculation type also uses the data of the feature itself it will also apply a lock for modifying the feature data. Since all locks applied to source features are shared locks any number of calculations can use the same source features at the same time. If locking on any source feature fails the execution of the calculated feature will fail.

If a calculation algorithm is based on another calculated feature and if that calculated feature is expanded that calculated feature will not be locked. Although locks are applied to all source features of the algorithm at the beginning of the algorithm execution, locks are removed as soon as the feature is not needed any more in the execution of the algorithm.