Building Distributed
Applications
Using the Progress AppServer
Progress Browse Design Considerations
In a 4GL client application, the Progress browse widget is bound to a query at compile time and controls record retrieval and presentation at run time.
In a traditional client/server application where a browse query satisfies a large number of records, the browse widget does not require all records to be delivered immediately; it caches some records not initially in the browse view port and, transparent to the user, requests additional records when the user scrolls to the end of the browse records. Therefore, there are no significant time delays relating to the delivery of a complete set of results prior to viewing data in the browse widget.
If browse data is to be retrieved from an AppServer, the following must occur:
This implies that if the remote query satisfies a large number of records, there might be a significant delay prior to viewing data in the browse widget. You might choose to accept this delay since once this delay is incurred no further network access is required. However, if this time behavior is unacceptable, consider choosing alternatives such as:
- Limiting the number of records that are delivered to the client application. For example, transfer only the first 200 records to the client application.
NOTE: This alternative assumes that the Application Server process building the original query is dedicated in state-reset or state-aware operating mode or is bound in stateless operating mode to the client application.- Creating your own caching and delivery scheme, using the APPEND option of temporary table parameters. For example, transfer to the client application the first 200 records and an indicator as to whether there are more records available. The client application can then notify the user that there are additional records available. If the user actually requires the additional records, the client application can request the next batch of records from the Application Server process, using the APPEND option, to add to the records that already have been transferred. See the Progress Programming Handbook for information about the APPEND option of temporary table parameters.
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