I could be termed a pipe stress analyst but my fort is the static analysis part.
But my job demand is tending towards the dynamic area, hence this enquiries.

(1). Is the Dynamic Load Factor(DLF) versus Natural Frequency graph generated by CAESAR II, an indication how the piping system (under analysis) mode of vibration would respond under time variant impact loads? A confirmation needed.

(2). And if (1) holds true, does the region of zero acceleration in the graph give a pointer to the obtaining the "the cut-off frequency" to be specified for further analysis?

(3) And if not, what exactly is the essence of generating the DLF spectrum graph before any analysis?

(4). Is there any text, that can give sufficient understanding? For now, I make do with CAESAR's manuals (technical, application guide etc)

(1) Rather than an indication of how a system would respond to an inpact load, I see the DLF vs. Frequency plot an indicator of the frequency content of the applied load. So for any system, or for any mode of vibration, a DLF is provided. I guess in a way we are saying the same thing.
(2) There is no zero acceleration in the plot mentioned. We suggest you set you cutoff frequency beyond the peak of the DLF vs. Frequency plot to be conservative.
(3) You can gain insight into the propensity of the system's modal response to an impulse. This DLF is one of the modal multipliers. Also, this is a vital piece of input for force response spectrum analysis.
(4) I have no addtional text to offer.