Message 'Material is blocked'
The system issues this message during collective delivery processing ifa material cannot be blocked during the creation of a delivery (SAPblock / enqueue).

Reason
Another user or the same user who works in two sessions carries out abusiness transaction (order, another collective delivery run) and blocksthis material, too.

Alternative
If parallel business transactions are also collective runs and if thesystem issues this error message frequently (e.g. material M1 is inevery delivery), you cannot use parallel processing.