Tobias, I'm a great fan of RAID-0 datasets (dataset striping) and the benefits of LSR buffering.
They are two very different things though, and if you would like to understand the benefit of each technique you may want to measure them separately. Data Set striping does two things. It flattens skew and increases parallelism. The benefit Data set striping may go unnoticed unless you run some background IO to create contention, or run multiple jobs reading the same dataset. For datasets converted from NSR to LSR I usually find that the major benefit comes from the buffering of the Index Set for a KSDS with three or more index levels. You may want to create some KSDS with one, two and three levels and compare your results with and without LSR. If the dataset has the VSAM defaults then the three level index will probably realize a 50-67% reduction in IO because of LSR. However if NSR is specified with BUFNI=INDEX-Set+1 the LSR performance benefit will be much smaller. In one shop I used ACC-SRS to force BUFNI=8 into the JCL of every KSDS allocation which cancelled most of the benefit expected from LSR buffering. A typical symptom to look for is a KSDS where IO count to the Index is three or more times the IO count to the Data. This is a sure sign of three level index, or greater, that is reloading the Index Set and a good target for SMB, BLSR, or some old fashioned Index buffers. It would definitely make for a good test program for your experiments. It is likely that optimizing this IO challenge will discount the benefit of dataset striping. Ron > -----Original Message----- > From: IBM Mainframe Discussion List [mailto:[email protected]] On Behalf Of > Tobias Cafiero > Sent: Wednesday, September 15, 2010 8:17 AM > To: [email protected] > Subject: Re: [IBM-MAIN] DFSMS and System Managed Buffering > > Ron, > I was expecting results similiar to the ones I saw in VSAM Demystified. > Instead of using Repro, I'll write something to do my testing. We will be > using > Dataset Striping and I am interested in putting them together. > > Tob > > ---------------------------------------------------------------------- > 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
