Patent ID: 8244913

Claim:
A method for monitoring data replication in a database system having an originating site and a plurality of target sites, the method comprising: sending a pulse from the originating site to one or more target sites of the plurality of target sites; receiving, by the originating site, (1) one or more echoes created by the one or more target sites of the plurality of target sites responsive to the pulse from the originating site, the one or more echoes associated with the pulse for which it is responsive to, each of the one or more target sites creating one of the one or more echoes and (2) data included in the one or more echoes describing one or more echo creation times for the one or more echoes, each of the one or more echoes including data describing a current pulse identifier uniquely identifying the pulse for which the echo is responsive to; and determining a site horizon based at least in part on an echo table including one or more rows, each row including data describing: a pulse identifier uniquely identifying an associated pulse; a site combination including an originating site identifier and an echoing site identifier, the originating site identifier describing the site that originated a pulse identified by the pulse identifier, and the echoing site identifier describing the site that last sent an echo including data describing the pulse identifier; and an echo return timestamp describing the time when one of the one or more echoes was created, each echo return timestamp associated with a site combination and a pulse identifier, and wherein the site horizon is determined by (1) identifying one or more rows in the echo table as a matching set, the one or more rows storing the one or more site combinations associated with the current pulse identifier included in the received one or more echoes, each site combination having an associated echo return timestamp included in the matching set, and (2) selecting the earliest echo return timestamp from the matching set as the site horizon thereby indicating that all data changes made prior to the time indicated by the site horizon have been propagated in the database system.