Thanks to all for taking the time to give such nice comprehensive answers to my questions!
John Krew ----- Original Message ----- From: "Bill Manry" <[EMAIL PROTECTED]> Newsgroups: bit.listserv.ibm-main To: <[email protected]> Sent: Tuesday, October 18, 2005 11:27 PM Subject: Re: IARVSERV > John Krew wrote: > >I was wondering if anybody on the list has had any experience using > >the IARVSERV macro for sharing data among address/data spaces. > > Oracle on z/OS uses it, specifically to share the database server's > "global" memory across multiple address spaces that also house client > sessions. This is a horizontal scaling feature. (Since Oracle is written > in portable C we can't use ALETs directly for horizontal sharing, and > of course we didn't want to use global memory like CSA.) > > I have a few bits to add to the others' replies. IARVSERV was > invented to support, and underlies, POSIX shared memory provided > by UNIX System Services. Using the C/UNIX/BPX interface to > this service is somewhat easier but requires that you be a POSIX > process (if you aren't, you get dubbed). If you use IARVSERV > directly there are two ways to use it, but only one of them is GUPI, > namely page-level sharing. If you are sharing a lot of memory there > is considerable overhead in MVS SQA--that's real memory and a > chunk of everyone's address space topography--for maintaining page > mapping tables. The overhead is 32 bytes of SQA per shared page > per sharing address space. The non-GUPI interface provides sharing > of whole 1Mb segments without the onerous SQA cost but it imposes > a heavy recovery burden on your application and likely would not be > considered supported by IBM. > > I believe some of the above is changed/improved for 64-bit applications. > > Would either systems _or_ applications programmers use IARVSERV? > I doubt it, except indirectly by those porting or writing UNIX-type > applications > and using one of the BPX interfaces. We found a good use for it, but > Oracle's > situation is somewhat unusual. > > /Bill Manry - Oracle Corp. > > ---------------------------------------------------------------------- > 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 > ---------------------------------------------------------------------- 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
