clist98.html

Cheryl's List #98 -
July 5, 2005

1. Cheryl Watson's TUNING Letter 2005 No. 3
2. The Fastest Computers in the World

1. Cheryl Watson's TUNING Letter 2005 No. 3

The forty-eight page 2005 No. 3 TUNING Letter was emailed to electronic subscribers last Thursday (30Jun2005). Single issues may be obtained for $135 each from our Web site at http://www.watsonwalker.com. The following is a summary of just some of the contents of this latest TUNING Letter:

PDSE Update
We have been very active over the last few months working with customers who have seen a dramatic increase in CPU consumption when using PDSE data sets. Cheryl first talked about this during her Hot Flashes session at SHARE in Anaheim, and then we had a more detailed summary in the last issue (see TUNING Letter 2005 No. 2, pages 30-36). Since then we have spent a good deal of time working with IBM in terms of getting their documentation up to date. The result is not as good as we had hoped, but all of the information seems to be out there if you dig for it a little. Our update on page 30 provides all of the details.

GRS Resource Name Lists
One of the most important operating system components is GRS because it serves as the gatekeeper to important system resources. Configuring GRS incorrectly can lead to performance problems as well as damage to your data. If you are using a GRSPlex (multiple images or LPARs that use GRS to manage the same resources), you should also be using the Resource Name List (RNL) feature of GRS. Using RNL correctly will improve performance, increase the integrity of your data and reduce the probability of deadlocks. See our article on page 37 for more information on the RNL feature, including details about some recent enhancements that make it even more powerful.

VSAM Data Sets
We were recently involved in a dispute between a user and IBM regarding the reporting of questionable VSAM statistics. IBM had changed the output of the popular IDCAMS program so that some statistics would not be displayed if a VSAM data set was not closed properly. This did not please the user because the change caused one of his production programs to perform poorly. The user argued that it was better to have incorrect statistics than no statistics at all. We think they were able to reach a compromise that satisfied the user and will be better for all of our readers. See the details on page 32.

On page 4 we mention a fix that allows obsolete VSAM attributes to be removed from a data set when you use IDCAMS to export and import it. Installing this fix now will give you a head start on correcting these data sets while it can be done easily (i.e. in the future, IDCAMS and application programs might not be able to even open them).

z/OS 1.7
This latest release of the popular IBM z/OS operating system will be available in September. This is the first z/OS release since IBM changed their policy to having a new z/OS release once per year, rather than once every six months. This means that there will be more demand for this release, and that it will contain more features than usual. Our preview on page 14 highlights the popular features and will help you prepare for installation of this important release. Also see page 43 for the latest IBM statements of direction. It is important that you pay attention to these so that you know what changes will be coming in the next few years.

2. The Fastest Computers in the World

The Top 500 Web site (http://www.top500.org) maintains a list of the 500 fastest computers in the world. This project was started in 1993 in an effort to maintain an ongoing list of the world's fastest processors. Twice per year they use the Linpack benchmark to rank each of the tested machines. Then they update and revise their Top 500 list. The current list was compiled by several supercomputing experts: Jack Dongarra from the University of Tennessee, Erich Strohmaier and Horst Simon from NERSC/Lawrence Berkeley National Laboratory and Hans Meuer of the University of Mannheim in Germany.

Here are the companies with the highest number of entries on the current Top 500 list:

http://www.ibm.com/press/PressServletForm.wss?TemplateName=

ShowPressReleaseTemplate&SelectString=t1.docunid=7753

Considering that each Teraflop represents a trillion floating point operations in one second, these machines have come a long way from your father's S/360.

Stay tuned!

Cheryl Watson
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