<P> For example, if an integrator (company) is providing an enhancement to a customer's existing solution, then they integrate the new application layer and the new database layer with the customer's existing application and database layers . After the integration is complete, users use both the new part (extended part) and old part (pre-existing part) of the integrated application to update data . A process should exist to exchange data imports and exports between the two data layers . This data exchange process should keep both systems up - to - date . The purpose of system integration testing is to ensure all parts of these systems successfully co-exist and exchange data where necessary . </P> <P> There may be more parties in the integration, for example the primary customer (consumer) can have their own customers; there may be also multiple providers . </P> <Table> <Tr> <Td> </Td> <Td> This article contains instructions, advice, or how - to content . The purpose of Wikipedia is to present facts, not to train . Please help improve this article either by rewriting the how - to content or by moving it to Wikiversity, Wikibooks or Wikivoyage . (November 2011) </Td> </Tr> </Table> <Tr> <Td> </Td> <Td> This article contains instructions, advice, or how - to content . The purpose of Wikipedia is to present facts, not to train . Please help improve this article either by rewriting the how - to content or by moving it to Wikiversity, Wikibooks or Wikivoyage . (November 2011) </Td> </Tr>

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