Insight 204 Register TODAY! Hotel deadline approaching!
By Marie Kelly
If you have yet to register for Insight 204 being held in Boston on September 17-20, don’t delay any longer! The deadline for the special hotel rate is August 13th, and seats are filling up FAST for the special training workshops being held on the last day of the symposium.
v To register for Insight 204 and secure a spot in the workshops of your choice, visit http://www.cca-int.com/usergroups/insight/forms/register.html TODAY. v To guarantee the reduced hotel rate, make your hotel reservation by August 13th. Visit http://www.cca-int.com/usergroups/insight/lodging.html for hotel contact information.
v To register for Insight 204 and secure a spot in the workshops of your choice, visit http://www.cca-int.com/usergroups/insight/forms/register.html TODAY.
v To guarantee the reduced hotel rate, make your hotel reservation by August 13th. Visit http://www.cca-int.com/usergroups/insight/lodging.html for hotel contact information.
Preparing for Insight 204 in advance
Want to get the most out of Insight 204? Read the abstracts presented on the Insight 204 Web site for General, Breakout, and Training sessions, and know in advance what sessions you absolutely do not want to miss!
This year's symposium features recurring favorite presentations such as the Customer Survey Results and Jim Damon's famous Performance Report. And of course, with a new version of Model 204 released last spring, numerous other presentation are focused on Version 5.1 to help you:
v Get the most out of new performance features that make Model 204 more reliable and faster than ever. v Connect Model 204 data and applications to any other environment within your IT infrastructure, including the Internet and non-mainframe systems.
v Get the most out of new performance features that make Model 204 more reliable and faster than ever.
v Connect Model 204 data and applications to any other environment within your IT infrastructure, including the Internet and non-mainframe systems.
Participating in Insight 204 in advance
The results of the 2002 Model 204 Customer Survey will be presented at this year's Insight 204. There are only a few weeks left for you to participate! Make your wishes known. Help develop Model 204 in ways that help you do your job.
Model 204 Version 5.1: New and Enhanced MONITOR Commands
By James Damon
Model 204 V5R1 became commercially available in March of this year and now runs in production at a number of customer sites. Customers report very positive results so far and few problems. We are extremely pleased with these initial reports. We will be discussing Version 5.1 in great detail at this year’s Insight 204 conference in Boston, which begins September 17th. Please see our web site for registration details.
One of the important changes you will find in Version 5.1 is improved system monitoring. We introduced several new MONITOR commands and enhanced others. The new commands are:
We also enhanced the output from:
Introducing the MONITOR CFR Command
The MONITOR CFR command was implemented to detect and monitor conflicts between users, who attempt to acquire critical file resource locks. The four critical file resources are INDEX, EXISTS, DIRECT and RECENQ. Each file has these resources, which correspond, respectively, to the Ordered Index, the existence bit maps, Table B, and the record enqueuing table.
When accessing a resource for read-only, it must be acquired in SHR mode; when accessing a resource for update, it must be acquired exclusively. These resources are usually held for exceptionally short periods of time, seldom exceeding a few microseconds.
Taking a Long Walk
However, the one, lengthy exception to the time a resource is held is a FIND statement that performs a long walk through the Ordered Index. The most extreme example of this is the following:
A leading-wildcard pattern compares every value of LASTNAME in the Ordered Index to the pattern. During the comparison, the FIND statement acquires a SHR lock against the INDEX resource, which prevents updates to any ordered field until the comparison is complete. To correctly evaluate the FIND statement, the Ordered Index must be static, not a moving, changing target.
If there are thousands or tens of thousands of values for LASTNAME, the comparison may take a significant amount of elapsed time to complete. During this time, a user, who attempts to update any ordered field in this file is placed in a wait state, which is indicated by WT=24 in the MONITOR CRF command output.
Detecting Critical File Resource Conflicts
Consider the following example. Four users, Zorro, Grumpy, Spiderman and Merlin, have called complaining that their sessions seem to be hung. They say they have not gotten a response back from Model 204 for at least ten minutes.
You issue a MONITOR FILES command and see the following:
Figure 1. MONITOR FILES command output
You will note that the four callers are in wait state 24 (WT=24) and each is trying to access file ACCT8. Also, note that user Gollum is accessing file ACCT8, but not in a wait state. In Version 5.1, using the MONITOR CFR command, you also see the following output, which indicates that the other four users are the victims of whatever Gollum is doing:
Figure 2. MONITOR CFR command output
From this MONITOR CFR display in Figure 2 you note that Gollum acquired the index resource against file ACCT8 at 18:07 and the current time is 18:21. Gollum has held the resource for the last 14 minutes, which prevents updates to any ordered field in file ACCT8. The four other users are probably waiting to perform various modest updates to ordered fields in that file, but are blocked by Gollum. You suspect that this processing is taking a long walk through the Ordered Index. You can look at Gollum's work more closely by issuing a MONITOR (79) SL command, which reveals the following:
Figure 3. MONITOR SL command output
GOLLUM
0
In the Figure 3 display of the MONITOR SL command, the DKRD statistic has a high value of 89,453. You suspect that the procedure, CUSTP.FINDNAME, is probably evaluating a FIND statement, which performs a long walk of the Ordered Index. The very high DKRD count tends to support this supposition. You must review and modify the procedure to reduce the number of values examined in the FIND statement.
Coming Attractions
I’ll discuss the other MONITOR commands and enhancements in future CCAprint articles. In the meantime, please make arrangements to join us at the second Insight 204 conference in Boston in September where we will be discussing all of the new, powerful features and enhancements available in Version 5.1. Hope to see you there!
System 1032 Views and News
By the Editor
Our long-time System 1032 writer, Tym Stegner, is on vacation for this August issue of CCAprint. We expect to see him back at his keyboard in time for the September edition.
Tym Stegner
Tym requests that if you have any topics you would like clarified or explained, or a problem application you would like discussed, just drop him a line.
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