Data Change Notification Interface

Data change notification (DCN) provides an HTTP interface by which enterprise information system (EIS) changes can immediately be propagated to Unwired Server.

All DCN commands support both GET and POST methods. The EIS developer creates and sends a DCN to Unwired Server through HTTP GET or POST operations. The portion of the DCN command parameters that come after http://host:8000/dcn/DCNServlet can all be in POST, or any var=name can be in either the URL (GET) or in the POST. The authenticate.password parameter is an especially good candidate for including in the POST method, as well as any sensitive data provided for attributes and parameters because the HTTP POST method is more secure than HTTP GET methods. See Developers Reference: Server API.

Note: Enter the HTTP request on a single line.

You must be familiar with the EIS data source from which the DCN is issued. DCNs can be created and sent based on:

Database triggers
EIS system events
External integration processes

You can use DCN with or without payload to instruct Unwired Server to refresh data:

DCN without payload – can only call MBO operations, and the name used in the DCN request must match that of the MBO definition:
1. The DCN requester (which may or may not be the EIS for DCN) sends an MBO operation execution request, along with operation parameters, to Unwired Server.
2. Unwired Server executes the operation, (effectively calling the EIS operation), and updates the consolidated database (CDB), if needed, depending on the operation's Cache Update Policy.
3. Unwired Server returns a DCN status message to the requester.
Note: Be careful when naming MBO operations in Unwired WorkSpace. If "delete" is the name of the EIS effecting MBO operation, it can easily be confused with the direct cache-effecting operation named :delete.
DCN with payload – calls only the two direct cache-effecting operations (:upsert or :delete), which always exist for an MBO, and are not related to user defined MBO operations.
- :upsert – the message must contain name/value pairs for every required attribute, and the name must match the MBO attribute name exactly.
- :delete – only the name/value pairs for the primary key column(s) need to be provided.
These operations insert/update a row in the CDB or delete a row from the CDB. Calling either of these operations does not trigger any other refresh action:
1. Some event initiates the DCN request (a database trigger for example).
2. The Unwired Server cache is updated directly from the EIS. The actual data (payload) is applied to the cache, through either an :upsert (update or insert) or a :delete operation.
3. Unwired Server returns a DCN status message to the requester.