This is the First activity in the sales Order line flow and mark as "Start" activity and it got triggered when we create an Order line .
When ever a new line created in an order that is in ENTERED status, order line workflow got created and in the staus BOOK_WAIT_FOR_H..Once we booked the order , work flow for the line progressed from this activity to next activity.
On the other hand if we entered order line in the already booked sales order , workflow for the line will not wait at this activity, rather will progressed immediately from this activity to next activity.
In case you have a case where order header is booked and 1 or more lines got Stuck at this activity ,then you have no option , but to progress the lines from these activity by means of
- RETRY this activity either from the workflow admin responsibility or
- With a datafix
In case we are using Oracle standard order line workflow there is no specific reason for lines workflow stuck at this activity .But many a time I found that this type of issue results if you have some system failure while you are processing the orders( like System Crash , Power Outage, memory issue).
But for a custom workflow I have noticed that many a time Order lines stuck at this activity , if activity after it is a custom one and it got error out.
And last but not the least I have notice that many a time line workflow stuck at this activity if order header workflow error during the booking process or while booking some sort of booking hold got applied on Order header.
That's my observations. Hope that help