MOBILE DATA BASES:

• Mobile Database' is either a stationary database that can be connected to by a mobile computing device - such as smart phones or PDAs - over a mobile network, or a database which is actually carried by the mobile device. This could be a list of contacts, price information, distance travelled, or any other information.
• Mobile database systems have to be adapted to the limited resources of current mobile devices.
• They are small-footprint databases, which use special replication and synchronization algorithms for the communication (up and download) with a centralized, consolidated and hard-wired database.
• A mobile database uses wireless technology to allow mobile computers to connect to its system.
• The database consists of a client and server that connect to each other over awireless network. Due to the vulnerability of wireless network signals, a cache of activity is maintained to ensure that sensitive information can be recovered.
• A mobile database is used to provide remote access to information that authorized users may need to obtain on a moment's notice.
• Mobile or cloud computing usually consists of three components.
• Base Stations: The Base stations are responsible for controlling the communication signals that need to be passed from one host to another. A base station receives and sends information and often comes in the form of some type of Wireless router.
• Hosts: They  are responsible for handling the actual transactions that occur within a mobile database. They are sometimes referred to as "fixed," since hosts do not typically change locations within the network. In order to process database requests, hosts use servers or software applications in order to access the data that is needed.
• Mobile unit:  These are the portable computers, phones and other devices that request information from the database. Rather than communicating directly with the database server, mobile units route their requests through the base stations.
• The various issues associated with mobile databases include the following:
• The relative unreliability of connections: The access between central servers and the mobile system may be unreliable at times.The disconnections that may occur can disrupt a query being performed and as a result, prevent or slow query response.
• The limitations on storage capacity: Due to the storage limitation of mobile computers, it is thus difficult to create replicas of large databases on such devices, particularly on handheld devices such as PDAs, which are the current focus of our work.
• The security and privacy issues created when a computer is in a mobile environment.
• Mobile database functionalities include the following
• Query processing and optimization
• Data Replication schema
• Concurrency controls
• Transaction support
• System recovery