>That leads to a question that I've been thinking about for some time. Since the 3390 geometry is emulated by modern storage control units, why then are the inefficiencies of small blocks emulated also? There are not SLEDs actually storing the data, why are IBG's, sectors, and all the other CKD nastiness emulated that makes 80 byte blocks such a bad idea? IOW, why can't the control unit simply store 708 * 80 byte blocks on a 56,664 byte 3390 track? Does zos's calculations take these inefficiencies into account and only write 78 of these blocks per track?
The "C" in CKD stands for "count" and this is some information about the amount of data following in the next data block (the amount may vary from block to block). Likewise "K" in CKD stands for "key" and some access methods are using key data that is stored before the actual data. So, both are bits of information that are used and thus cannot be dropped. -- Peter Hunkeler ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
