Actually, in it's original form (on 3090 or 9021, IIRC), Expanded storage was physically different memory. It was slower, and therefore cheaper. As real storage got cheaper, it was positioned as a paging-avoidance mechanism until the OS could be enhanced to address more real storage.
HDS used the fact that their memory was all the same, and you could move the line between types at will, as a selling point. -----Original Message----- From: Linux on 390 Port [mailto:[EMAIL PROTECTED] On Behalf Of Mark Perry Sent: Friday, November 03, 2006 1:42 PM To: [email protected] Subject: Re: [LINUX-390] Central vs Expanded Storage * PGP Signed by an unknown key: 11/03/2006 at 01:42:26 PM Hi Steve, the faster option is "not to page", which is an option if you have more real memory i.e. Central storage. Paging *OUT* from Expanded Memory, if I understand correctly, requires first bringing the data into Central storage so that it can then be written to DASD. If Expanded storage offered a better paging solution then don't you think z/OS would have retained support for it? Expanded storage, I believe, originated as physically separate storage in the days before 64bit addressing. The z9 no longer has such limitations. Sorry I didn't want a rehash, and yes I will search the archives (a pointer would have been nice.) Mark Steve Gentry wrote: > Mark, respectfully, this has been hashed over many times, even recently. > Check the archives. > Think about it, which would it be faster to page from extended storage, > which is memory or a disk drive, which is going to be > slower? If you allocated all to real and you still had to page, then > you'd by pass the extended storage and go straight to dasd. > There are others here who can go into far more technical details about the > "internals" of VM and why it likes extended storage. > I think the consensus from the group and even IBM is to define some > extended storage. > Hope this helps a little. > Regards, > Steve G * Unknown Key * 0x14419D74 (L) ---------------------------------------------------------------------- For LINUX-390 subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 -------------------------------------------------------- If you are not an intended recipient of this e-mail, please notify the sender, delete it and do not read, act upon, print, disclose, copy, retain or redistribute it. Click here for important additional terms relating to this e-mail. http://www.ml.com/email_terms/ -------------------------------------------------------- ---------------------------------------------------------------------- For LINUX-390 subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390
