Also, remember that for Hiperbatch only the Data component is kept in the DLF object. So you would still have to deal with I/Os to the index. You can provide enough buffers to keep the index set in storage but you don't get lookaside on the sequence set. With BLSR, you can avoid the seqence set I/Os too. So you have to see which is going to provide the greater benefit, eliminating all of the data I/Os with Hiperbatch, or eliminating more index I/Os (and hopefully some data I/Os) with BLSR. Which provides greater benefit is going to depend on the reference patterns of the jobs accessing the file (that's a fancy way of saying YMMV!). :-)
Have a nice day, Dave Betten DFSORT Development, Performance Lead IBM Corporation email: [EMAIL PROTECTED] DFSORT/MVSontheweb at http://www.ibm.com/storage/dfsort/ IBM Mainframe Discussion List <IBM-MAIN@BAMA.UA.EDU> wrote on 11/12/2007 07:44:59 AM: > Alex Tough asked: > > > If you have all or most of the cluster allocated to a DLF data > > object, why would BLSR be faster ? > > It might depend on what you mean by "faster"... > > Note that nowadays a DLF (or any) hiperspace would be backed by central > but would still require a more distant data movement. And, in principle, > VSAM LSR (whether via BLSR or not) ought to be in the job's own address > space. So, in CPU terms I'd speculate that BLSR might cost less CPU. That > probably wouldn't turn into elapsed time differences that were measurable > - but it just MIGHT. > > Another thing to remember, though, is that Hiperbatch keeps the memory > "pro bono publico" whereas BLSR doesn't. The affordability of Hiperbatch > may be much greater for CONCURRENT jobs. In the same vein with multiple > BLSR jobs each job would have to populate the buffer pool itself. So > initially you might get a lot of misses. > > All a long-winded way of saying "YMMV". :-) > > Cheers, Martin > > Martin Packer > Performance Consultant > IBM United Kingdom Ltd > +44-20-8832-5167 > +44-7802-245-584 > [EMAIL PROTECTED] > > > > > > > > > > > Unless stated otherwise above: > IBM United Kingdom Limited - Registered in England and Wales with number > 741598. > Registered office: PO Box 41, North Harbour, Portsmouth, Hampshire PO6 3AU > > > > > > > ---------------------------------------------------------------------- > 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
