On Tue, 11 Apr 2017 16:45:10 -0500, Greg Dyck wrote: >On 4/11/2017 3:26 PM, Paul Gilmartin wrote: >> My understanding, ancient, probably outdated, and certainly naive is that >> there is little communication between GETMAIN/FREEMAIN and the paging >> subsystem. If a program touches a page that was never GETMAINed no error >> occurs; simply a page slot is allocated up to the limit of the REGION >> parameter. Conversely, on FREEMAIN the page slots are not released. > >*Totally* wrong. z/OS (or any predecessors or relatives like VS1) has >never worked like you describe. > >If a virtual page is not 'getmain assigned' by VSM it will never be >backed by a real frame by RSM and an 0C4-11 will occur. When all >virtual storage on a page is freed VSM will return the allocated AUX >slot and real frame, if either have been allocated, and reset the >'getmain assigned' indicator. > What about the other side? Will GETMAIN return indication of success only if the requested page slots can be committed?
A Google search for "lazy malloc" shows the preponderance of complaints concern Linux. My information came from a UNIX/C programmer before the ascendancy of Linux. And from an MVS wizard who insisted that for GETMAIN to fail if requested page slots could not be committed would cause enormous breakage of existing art. -- gil ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
