There was a Redbook entitled 'Partitioned Data Set Extended Usage Guide', document number SG24-6106-01, dated May 2005 (so it very much pre-dated PDSE V2).
That Redbook stated that that PDSE directories entries were organised in a balanced B-tree, and that the PDSE pages were either directory pages, or data pages, not mixed. That information may no longer be accurate, of course. I say was, as I searched on the Redbooks site in an effort to provide a link, using both the document title and number as search terms, but didn't find it. Ant. -----Original Message----- Subject: Re: Maximum size of a PDSE library? On Tue, 21 Feb 2017 00:10:42 -0600, Barbara Nitz wrote: > >I believe that inserting an entry is just finding the place where it belongs >and adjusting the previous and next pointer(s). > IOW you believe its a linear linked list rather than such as a B-tree? Ouch. Are the directories for PDSEv1, PDSEv2, HFS, and ZFS similarly organized? Probably NDA. >As for caching: The SMSPDSE1 address space used to cache the 4K blocks. Which >did not help at all, because back then the maximum cache available to SMSPDSE1 >was 16GB (I believe). We had about 10 of those large VB PDSE's, and together >they were much bigger than the available cache, and SMSPDSE1 would cache the >full 4K (which includes data). ... > You suggest directory blocks contain data? That would seem to optimize space utilization at the expense of performance. And gain little except for quite small members. And if I NOTE at the millionth record of the thousandth member of a VB PDSE and later POINT to it, I wonder what processing occurs? Probably NDA. -- gil ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
