When streaming is enabled, files that are downloaded with the binary macro are not loaded in memory before they are sent to the output device but they are streamed directly from disk or from the database to the network stream. This has a few consequences:

• Because the files are not loaded in the memory before they are sent to the client, less memory is needed, especially when downloading large files.
• The SXML rendering is bypassed. When streaming is set to false, the binary data of the item is set as the result of the module and normal SXML rendering proceeds which means that you have the ability to perform extra logic on the result of the binary macro. However, when SXML rendering is bypassed the binary data is sent to the client before the macro execution ends.
• When using streaming, a new stream is opened for every request to either a database or file. This is fine for large files where the download takes up more time than opening the stream but for small files like icons or small images, this degrades performance. For small files/images it is better to set streaming to false.

When using streaming, you should also using the cachefile macro to cache the output. This solves the performance issue caused by the need to open the streams for every request.