Cheryl's List #60 -
January 9, 2002
 |
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1. Updates
2. Cheryl Watson's TUNING Letter 2001, No. 6 Summary
3. CD-ROM
4. Vacation Time
1. Updates
a. Here is an update for our 2001, No. 6 TUNING Letter: On page 35, in Figure 19, the last line shows a % increase in size of 0.2142. It should be 21.42. This will be corrected in the hard copy and CD-ROM, but is incorrect in the electronic version.
b. Jerry Urbaniak of Acxiom CDC Inc. pointed out
that APAR OW45117 was finally closed on 11/27/01 for OS/390 R6 and
later. (It was opened 6/21/00.) This APAR described a situation
where higher importance server address spaces may be delayed by lower importance
work. Running in WLM goal mode and classifying CICS or IMS transactions,
on a CPU-constrained system it is possible for higher importance server
regions to be delayed by lower importance work. The problem is most
likely to occur when there is only one service class defined for the subsystem
so all transactions for that subsystem are running in the same service
class. We noted this APAR in Cheryl's List #45 (July 18, 2000) and
our 2000, No. 4 TUNING Letter issue (on page 25). This is a good
fix to apply in order to protect your important online systems. It
only applies if you have assigned service classes to the transactions in
the CICS or IMS classification rules.
2. Cheryl Watson's TUNING Letter 2001, No. 6 Summary
The forty-four page 2001, No. 6 TUNING Letter was emailed to electronic subscribers on Tuesday, January 8. The issue will be mailed to print subscribers on or before January 21st. Here are a few of the topics we covered, taken from our "Management Issues." You can purchase a printed copy of the current TUNING Letter for $85.
Virtual Storage
Virtual tape subsystems provide a hardware and software solution to
inefficient tape processing. The benefits from these systems led
many people to IBM's Virtual Tape System (VTS). Now, StorageTek has
a new subsystem out that is similar but different enough to deserve its
own article. Ned Diehl, of The Information Systems Manager,
Inc., wrote an in-depth article on virtual tape systems featuring IBM's
VTS for our 2000, No. 5 TUNING Letter. He follows up in this issue
with a description of STK's new Virtual Storage Manager (VSM), including
recommendations on how to analyze the VSM data. See page 13.
As an aside, there is a current flash warning about the invalidity of some
of the data presented by IBM's VTS. See page 9.
CICS V4 vs TS Performance
A common question is "what is the overhead or savings when going from
CICS V4 to CICS TS?" While it's possible to see a 7-8% CPU increase,
there can also be some significant savings, especially if you're using
DB2. Bob Archambeault answers the question starting on page
35.
Fewer But Faster CPs
The most frequent question I'm asked is "does it hurt to go to fewer
but faster CPs?" The answer is "it depends," and there can be some
negative results. It's still possible for a single, high-importance
or high priority, job to run away with the system at the expense of the
lower importance work. As more people are moving to the 250 MIPS
z900 machines, the situation of moving to a few fast CPs from several slower
CPs is becoming even more common. See my discussion on page 40.
Elsewhere in This Issue
In our News section on page 4, these topics are covered: BMC manuals
online availability, a pointer to an article describing migration considerations
for CICS V4 to CICS TS, response to some VTS questions, a follow-up on
WAS 3.5, a news report showing IBM as number one in the worldwide server
market, some Hiper APARs, an article about SCEERUN and high I/O activity,
a summary of WSC flashes and white papers, a note that TalkLink has been
discontinued, and a note about some IBM URLs that have changed. In
our CICS Performance Tips on page 36, we discuss why CICS TS 1.3 writes
more SMF data and how you can deal with it. Our Q&A on page 40
shows how you can reduce overhead in CICS running under WLM. Bob
Shannon provides a technique for coding without base registers on 64-bit
machines (page 28).
3. CD-ROM
The fourth edition of our CD-ROM (containing all material published
from 1991 through 2001) will be shipped to active electronic subscribers
in February. Note: I had planned to complete the WebSphere two-part
series in the No. 6 issue, but we're still waiting for some required information.
Because we need to get this issue onto the CD-ROM, we've delayed the WebSphere
article until the next issue (mid-February).
4. Vacation Time
We're off to the Amazon from January 26 to February 8! We'll spend most of the time on the river, and then it's on to Machu Pichu. There will be no computer access for two weeks! Linda May will be monitoring our email, but it's important to send queries only to admin@watsonwalker.com or support@watsonwalker.com. BoxScore support is being provided by another person while we're out of touch. We have our shots and malaria pills, so I guess we're good to go!
Stay tuned!
Cheryl Watson and Tom Walker
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