In this paper, the various mechanisms used for concurrency control in a distributed database are summarized and their respective advantages and disadvantages are listed. Distributed databases have become a large part of the current information era. Millions of users access the data stored on these databases at a time. This simultaneous access by multiple users may lead to update problems and hence access must be controlled. The concurrency control mechanisms in a database control simultaneous access to a particular data or data set. © Research India Publications.