A method and apparatus in a data controller in a storage drive for retrieving, evaluating, and processing a context that describes a direct memory access (DMA) request. The data controller includes a buffer for storing data transferred in response to execution of a DMA transfer request, a host address pointer pointing to a current location in the buffer, and a retrieval channel device. The retrieval channel device is configured to: fetch a context that describes a DMA transfer requested by a host computer, determine whether a current capacity of the buffer for transferring data exceeds a threshold, generate an instruction to transfer a second amount of data to complete at least a portion of the requested DMA transfer if the current capacity does exceed the threshold, assert the instruction generated by the retrieval channel device, and adjust the host address pointer by the second amount of data.