When DisableChunkUpload is set to true file is uploaded at once into the memory and it does not exists on the file system. When DisableChunkUpload is set to false file is uploaded on chunks. All chunks are written in the temp file. Size of chunks is controlled by ChunkSize property.
Note that in both cases Handler's Process method is called once after the file is uploaded in the memory or after it is uploaded in the temp folder.
For larger files try to add MaxFileSize for the RadAsyncUpload or increase the execution timeout.
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