I think there is a DCB parm NCP or "Number of Channel Programs" that impacts the relationship between buffers and SIOs.
In many cases it is some what of a mute issue ... most DASD hardware reads a track at a time into chache effective many years ago. Tape does hardware level compression and physical block size on tape has little or nothing to do with DCB options ... etc ---------------------------------------------------------------------- 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
