The opposing requirements of consistency and maximum concurrency must be harmonized for the processing of master-detail structures in OLTP applications.
If, for example, all items ordered by a particular customer are locked during the processing of an order operation, all the other order operations will be blocked. If the customer row is released after each order item, it can happen that the input of order items that are still open is blocked by the simultaneous processing of other orders made by the same customer.
For this reason, ADABAS provides a transaction chaining via the KEEP LOCK option in the COMMIT statement. Such a transaction chaining allows a user to perform a COMMIT at the end of a transaction and to extend simultaneously some of the locks (typically those on the master row) to the next transaction.