No, I'm not on some strange medication. In any situation where multiple mobile databases are used or where there is a home-base database, you require replication to synchronize the data and operations between these databases. Our traveling salesman dials his head office nightly to download new product information and new marketing collateral and upload sales and order data to the head office's database. Our botanist makes a radio or satellite link-up to her base laboratory to replicate her sighting data to the laboratory database. In this month's column, the second in my miniseries on mobile databases, I will review the concept of replication, various replication configurations, and issues related to managing replication in the mobile database context.
Replication Let's begin with an informal definition of replication.
Transaction-based replication means that an entire transaction is replicated to a specific target database, or not at all. A transaction is an atomic unit of processing on the source database. The effects of a partial transaction may leave the database in an inconsistent state. Thus, the operations propagated to any given target database must also adhere to the transaction boundaries and the transaction properties. For example, if a plant sighting is replicated from our botanist's desktop database to the base laboratory database, it should include the locality details that were recorded as part of the sighting.