PostgreSQL is a sophisticated Object-Relational DBMS, supporting almost all SQL constructs, including subselects, transactions, and user-defined types and functions. (See www.postgresql.org).
What's Asynchronous Replication
Data Replication is a process that allows to build a distributed database through the management of multiple copies of data, caching one copy on each site. In particular, synchronous replication (also called real-time data replication) conveys information in real time to all of the involved sites. On the contrary, asynchronous replication (also called store and forward data replication) stores operations performed on a database in a local queue for later distribution by a database synchronization process.
Synchronous replication technology ensures the highest level of data integrity but requires a permanent availability of servers and transmission bandwidth. On the other hand, asynchronous replication provides more flexibility than synchronous replication as a database synchronization time interval can be defined which can vary from minutes to months and, moreover, a single site could work even if a remote server is unreachable or down. In addition, data operations are performed more quickly and network traffic is more compact. However, a more complex replication planning is required in the case of asynchronous replication in order to detect and correct data conflicts due to concurrent modifications occurring at different sites between two database synchronization events.