I think a lot of shops use this strategy for managing the common/private boundary.
1. Look at a running system. 2. Verify that the system is happy with defined CSA/SQA. 3. Verify that the private area is 'satisfactory', i.e. not too small nor needlessly large. 4. Calculate the contribution to CSA/SQA that IEASYSxx values have added to the z/OS requirement. 5. Adjust the IEASYSxx values to the midpoint of the final 1M portion. Since the user specification will tweak the 1M boundary placement, we aim to maximize any possible fluctuation that will preserve the private area sweet spot. That is, allow for 512K up or down in z/OS calculation without changing private area, which many (most?) systems are most sensitive to. OP's problem after all is to explain a 1M drop in private, not a change to common. BTW I looked at my VSM health checks but did not see this information displayed starkly. . . . J.O.Skip Robinson Southern California Edison Company Electric Dragon Team Paddler SHARE MVS Program Co-Manager 626-302-7535 Office 323-715-0595 Mobile [email protected] -----Original Message----- From: IBM Mainframe Discussion List [mailto:[email protected]] On Behalf Of Peter Relson Sent: Saturday, August 29, 2015 6:55 AM To: [email protected] Subject: Re: Smaller Private Area in DR <snip> The real question is when the COMMON/PRIVATE boundary gets set. IODF must be read and digested very early in IPL, certainly before SYS1.PARMLIB is opened. By the time IEASYSxx is processed, do below-the-line UCBs figure into the boundary calculation? <end-snip> It works something like this: -- Load the nucleus. Thus we have a definition for where that starts and ends. -- Build things such as UCB's that require common storage (think of that as initial SQA) -- Read system parameters to see the definitions of SQA, CSA -- Now determine the boundary of SQA (multiple of 64K?) based on the initial SQA and the SQA specification -- Now build LPA -- Use the LPA boundaries and the CSA size to define the CSA boundaries (1M multiple?) -- That is when the Common/Private boundary is set Any differences in the "earlier" areas can affect the Common/Private boundary. I seem to recall (but might be wrong) that one of the VSM health checks reports on how close you are to the point where you will lose 1M of private. Peter Relson z/OS Core Technology Design ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
