1. A method for selecting and sending one or more transactions, from a set of transactions, for replication between database systems, comprising: receiving by a capturing process of a first database system, at a first time, a particular start transaction record; adding, by the capturing process, the particular start transaction record in a list, wherein the list comprises zero or more start transaction records that were added to the list before the particular start transaction record is added to the list; wherein each of the particular start transaction record and the zero or more start transaction records is a start transaction record for one of a subset of transactions in the first database system; wherein, when a subset of transactions makes a data change in the first database system that should be replicated in a second database system, (a) all start transaction records in the list are sent to one or more apply processes of a second database system and (b) all the start transaction records in the list are removed from the list; receiving by the capturing process, at a second time that is later than the first time, a particular end transaction record that signals an end of a transaction whose beginning is signaled by the particular start transaction record; determining, by the capturing process, whether the particular start transaction record still exists in the list; in response to determining that the particular start transaction record still exists in the list, performing: determining that there is no data change that should be replicated in the second database system following the particular start transaction record; and removing, by the capturing process, the particular start transaction record from the list; and in response to determining that the particular start transaction record does not exist in the list, performing: determining that data changes following the particular start transaction record have been sent in the second database system; and sending, by the capturing process, the particular end transaction record to the one or more apply processes; wherein the method is performed by one or more computing devices comprising a processor.