>From my research (and some Share presentations) my understanding is that, >prior to 2.3, z/OS reserved large frames at IPL time which would make them >unavailable for 4K pages unless the system broke them up.
Making LFAREA a limit rather than a reservation is much better. My question, essentially, is if there is any penalty for leaving LFAREA much higher than required. I'm asking because it's tempting to set some parameters artificially high so you don't have mess with them but there's a hidden cost. One example is CICS max task (MXT). A lot of shops set it to the max of 999 which causes WLM to waste a lot of CPU going through unused performance data blocks. Robert Crawford Mainframe Management United Services Automobile Association (210) 913-3822 « Des clochards comme nous, bébé nous sommes nés pour courir » - Voltaire Please send requests to mainframe management through our front door at go/mfmfrontdoor -----Original Message----- From: IBM Mainframe Discussion List <IBM-MAIN@LISTSERV.UA.EDU> On Behalf Of Harris Morgenstern Sent: Monday, March 29, 2021 9:34 AM To: IBM-MAIN@LISTSERV.UA.EDU Subject: EXTERNAL: Re: LFAREA in z/OS 2.3 Prior to V2R3 the specification of the 1M LFAREA resulted in storage being physically reserved for LFAREA frames (used to back IARV64 PAGEFRAMESIZE=1Meg requests), but which could potentially be used for other purposes. If the system ran low on memory, the 1M LFAREA could be used to satisfy non-LFAREA real storage requests. So even though the 1M LFAREA was a reservation, the reservation could be broken and so it might have behaved more like a limit. In V2R3 and above, the real storage management is more effective at reducing fragmentation, resulting in more available 1Meg units of real. The need for the 1M LFAREA (as a reservation) went away. Harris Morgenstern z/OS Storage Management and System REXX Dept. OBPA IBM Poughkeepsie 8-295-4221 hmor...@us.ibm.com ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
