NexusDB

The Client layer of NexusDB provides access to the data stored on the server. This layer is composed of the following components: TnxSession, TnxDatabase, TnxTable, and TnxQuery.  These components support the traditional Borland database paradigm and enable developers to use data-aware controls.

The session component represents a thread specific connection to the server. The session also provides the security context.  The TnxSession attaches directly to a server engine component, which may be a remote server engine or the actual server engine embedded within the same application.

A database specifies a particular server alias or alias path.  The TnxDatabase component is associated with a session component.  The TnxDatabase is not mandatory since the TnxTable and TnxQuery components allow the developer to specify the alias name directly.  For ease of maintenance, use of TnxDatabase is recommended.

Tables and queries are used to access the data in the database and are TDataSet descendants. TnxTable provides optimized navigational access to the underlying server table cursors.  TnxQuery supports ANSI standard SQL for data retrieval, modification and definition.  Both components support standard TDatasource components and data-aware controls.

The Client layer components interoperate in this way:

The client components work together to coordinate communications with their server side counter parts.  As illustrated there is a one to one correspondence between the client and the server's representation of that client.  If the server engine is within a separate process, all communications occur through the remoting layer.