> -----Original Message----- > From: IBM Mainframe Discussion List > [mailto:[EMAIL PROTECTED] On Behalf Of Thompson, Steve (SCI TW) > Sent: Tuesday, September 12, 2006 12:33 PM > To: [email protected] > Subject: Re: Question : VTOC size - JES2 Volume
<snip> > But a question occurs to me. Mind you, I haven't needed to do > this for a > while, but would JES2 even care if HASPACE was in tracks, started on > other than a CYL boundary and otherwise took up the volume? I ask this > because I haven't needed to write 3390 CCWs in many years, and so with > RAID devices backing things, is there really any performance hit for > non-CYL boundaries? > > Later, > Steve Thompson I think that most of the non-cylinder allocated dataset "problems" went away with ECKD. I remember in the past that if a dataset was non-cylinder allocated, then the CCW string used by ???? access method would not be able to use the "search this cylinder for the record" opcode, but would need to search each track individually because the dataset __might__ not end on a cylinder boundry. IIRC, with ECKD, the access method does a "define extent" to set up the range of tracks for I/O and the control unit will abort any attempt to get outside that extent. So the access method (just can't remember which one!) can feel free to use multitrack searching. -- John McKown Senior Systems Programmer HealthMarkets Keeping the Promise of Affordable Coverage Administrative Services Group Information Technology This message (including any attachments) contains confidential information intended for a specific individual and purpose, and its content is protected by law. If you are not the intended recipient, you should delete this message and are hereby notified that any disclosure, copying, or distribution of this transmission, or taking any action based on it, is strictly prohibited. ---------------------------------------------------------------------- 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
