In this paper, transactions models for mobile computing support as well as the challenges to be solved in order to make stronger it are detailed. Mobile computing is growing and its use on wireless portable devices -such as mobile phones, personal digital assistants and laptops- for transmission and information access is very frequent. Services are provided through base stations based on wireless networks. Mobility presents new challenges and novel transaction models are required to provide a flexible, robust and secure way for mobile frameworks. This work introduces basic concepts about transactions and its characteristics. Flat and distributed transaction models, most commonly supported by distinct DBMSs are introduced. Mobile transaction models for wireless devices are studied. The major troubles on transactions due to mobility characteristic of these emerging technologies are broadly discussed in addition to promising lines of research.