Optimistic Row-level Locking

From InterBase

Optimistic locks are applied only when a client actually updates data, instead of at the beginning of a transaction. InterBase uses optimistic locking technology to provide greater throughput of database operations for clients.

InterBase implements true row-level locks, to restrict changes only to the records of the database that a client changes; this is distinct from page-level locks, which restrict any arbitrary data that is stored physically nearby in the database. Row-level locks permit multiple clients to update data that is in the same table without coming into conflict. This results in greater throughput and less serialization of database operations.

InterBase also provides options for pessimistic table-level locking. See the Embedded SQL Guide for details.