A method of synchronizing data records stored in a device database and a host database (24A, 24B, 24C), wherein the device database is coupled to a portable data communication device, the method comprising the steps of: storing, at the host database (24A, 24B, 24C), a pair of synchronization parameters (34; 36) with each data record stored in the host database (24A, 24B, 24C), the pair including a first synchronization parameter (34; 36) in form of a version number associated with the device database, and a second synchronization parameter (34; 36) in form of a version number associated with the host database (24A, 24B, 24C); storing, at the device database, a pair of synchronization parameters (34; 36) with each data record stored in the device database, each pair including a first synchronization parameter (34; 36) in form of a version number associated with the device database, and a second synchronization parameter (34; 36) in form of a version number associated with the host database (24A, 24B, 24C); designating the host database (24A, 24B, 24C) as a master database and the device database as a slave database; updating a data record at the device database; at the device database, incrementing the first synchronization parameter (34; 36) of the updated data record at the device database; transmitting an update message from the device database to the host database (24A, 24B, 24C) via a wireless data network, the update message including the incremented first synchronization parameter (34; 36), the second synchronization parameter (34; 36), and the updated data record from the device database; receiving the update message at the host database (24A, 24B, 24C); and updating the data record at the host database (24A, 24B, 24C) using the information from the update message, subject to the second synchronization parameter of the device database, as received in the update message, being equal to the second synchronization parameter of the host database (24A, 24B, 24C) which indicates a version number of the data record at the host database (24A, 24B, 24C). storing, at the host database (24A, 24B, 24C), a pair of synchronization parameters (34; 36) with each data record stored in the host database (24A, 24B, 24C), the pair including a first synchronization parameter (34; 36) in form of a version number associated with the device database, and a second synchronization parameter (34; 36) in form of a version number associated with the host database (24A, 24B, 24C); storing, at the device database, a pair of synchronization parameters (34; 36) with each data record stored in the device database, each pair including a first synchronization parameter (34; 36) in form of a version number associated with the device database, and a second synchronization parameter (34; 36) in form of a version number associated with the host database (24A, 24B, 24C); designating the host database (24A, 24B, 24C) as a master database and the device database as a slave database; updating a data record at the device database; at the device database, incrementing the first synchronization parameter (34; 36) of the updated data record at the device database; transmitting an update message from the device database to the host database (24A, 24B, 24C) via a wireless data network, the update message including the incremented first synchronization parameter (34; 36), the second synchronization parameter (34; 36), and the updated data record from the device database; receiving the update message at the host database (24A, 24B, 24C); and updating the data record at the host database (24A, 24B, 24C) using the information from the update message, subject to the second synchronization parameter of the device database, as received in the update message, being equal to the second synchronization parameter of the host database (24A, 24B, 24C) which indicates a version number of the data record at the host database (24A, 24B, 24C).