At what stage in system development life cycle are all data documented in the form of detailed data flow diagrams(DFDs)

The system development life cycle moves through distinct phases, each producing its own type of documentation. A feasibility study checks whether a proposed system is worth pursuing at a high level, and system design takes an already-understood set of requirements and turns them into a detailed technical blueprint, such as file layouts and program specifications.

Before design can happen, the existing system and its data flow must be studied and recorded in depth. This is done during system analysis, where analysts investigate how data currently moves through the organisation and document it precisely using tools such as data flow diagrams, which map out the sources, processes, and destinations of every piece of data. Producing this detailed, diagram-based documentation of data movement is a defining activity of the analysis phase, not of feasibility study or design.

Associate data flow diagrams with the analysis stage, since their purpose is to capture how data currently flows before any new design decisions are made.