On 2 December 2010 18:20, Ron Hawkins <[email protected]> wrote: > Tony, > > You are surprised, and then you explain your surprise by agreeing with me. > I'm confused.
Well now I'm confused; I'm not sure how I did what you say. > I'm not sure if you realized that the Huffman encoding technique used by > DFMSdss COMPRESS keyword is not a dictionary based method, and has a > symmetrical CPU cost for compression and decompression. No, I didn't know anything about the compression methods triggered by these two keywords until this thread. But I do know to some extent how both Huffman and the LZW-style dictionary compression schemes work, and that there is a differential between encoding and decoding speed when an inherently adaptive scheme like LZW is used, vs a usually static Huffman scheme. But I'm afraid I'm missing your point. You said that the saving in hardware assisted compression is in decompression, and I took this to be a claim that hardware assisted decompression is somehow speeded up - when compared to a plain software implementation - relatively more than is compression, and I said that I doubt that that is the case. But if it is indeed the case under some circumstances, then I don't see why most shops would care in most cases. > Finally, as I mentioned in another email, there may be intrinsic Business > Continuance value in taking advantage of the asymmetric CPU cost to speed up > local recovery of an application, or Disaster Recovery that is based on > DFSMSdss restores. An improvement in Recovery time may be worth the > increased cost of the backup. It's certainly possible, but I think it is unlikely to be the common case. Tony H. ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
