DPMODE SET TO HIGH

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DPMODE SET TO HIGH
I am having problems with a DB2 CICS transaction the is using 80 % of the processor. Our CICS
person has all the transaction in the RCT DPMODE set to High. Could this our transaction to use
so much processor?


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Eric Pearson

Re: DPMODE SET TO HIGH
(in response to william.poston@DB.COM)
The total processor time used is a function of what the transaction is
doing.
The percent of CPU used at any given time is affected by several parameters:
CICS dispatching priority, DB2 dispatching priority, DPMODE, other workload
and its dispaching priority (or target velocity in WLM Goal Mode terms),
etc.

How long does the transaction run? How many CPU seconds (minutes? hours?)
does it use per iteration of the transaction?
If it uses 80% of a CPU and runs only a few seconds, you do not
have a serious problem, and might not have a problem at all. You could
adjust priorities to have it
use slightly less of a CPU for a slightly longer time (assuming that
there are other tasks wanting to use the CPU). If it uses 80% of a CPU and
runs several
hours, this transaction needs serious surgery.

Regards,
eric pearson
NS ITO Database Support


-----Original Message-----
From: William Poston [mailto:[login to unmask email]
Sent: Friday, December 14, 2001 10:32 AM
To: [login to unmask email]
Subject: Re: DPMODE SET TO HIGH


I am having problems with a DB2 CICS transaction the is using 80 % of the
processor. Our CICS
person has all the transaction in the RCT DPMODE set to High. Could this our
transaction to use
so much processor?


--

This e-mail may contain confidential and/or privileged information. If you
are not the intended recipient (or have received this e-mail in error)
please notify the sender immediately and destroy this e-mail. Any
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e-mail is strictly forbidden.








Joel Goldstein

Re: DPMODE SET TO HIGH
(in response to Eric Pearson)
Message text written by DB2 Data Base Discussion List
>
I am having problems with a DB2 CICS transaction the is using 80 % of the
processor. Our CICS
person has all the transaction in the RCT DPMODE set to High. Could this
our transaction to use
so much processor?<

Yes and no. This will allow the transaction to "get" more of the
processor/machine at any point
in time, cpmpared to other jobs/address spaces in the system.
However, if something is using excessive amounts of CPU you need to look at
the application
SQL and access paths.
Additionally, you need to look at the transaction volume, and the amount of
CPU/Tran.
Even efficient transactions can use a lot of total CPU when the volume is
high, and they
are using multiple threads for execution.

Regards,
Joel



[login to unmask email]

Re: DPMODE SET TO HIGH
(in response to Joel Goldstein)
Joel I looked at the access path and it looked pretty good except for a sort. Could that cause the problem?
The transaction count was very high when this was happening. Apparently because of the time of year a lot
of people was using the transaction and the transaction has scrolling (Users can page up and down on their
screen) . what do you think?

Thanks


---------------------------------------- Message History ----------------------------------------


From: Joel Goldstein <[login to unmask email]>@RYCI.COM> on 12/14/2001 11:52 AM EST

Please respond to DB2 Data Base Discussion List <[login to unmask email]>

DELEGATED - Sent by: DB2 Data Base Discussion [login to unmask email]>


To: [login to unmask email]
cc:
Subject: Re: DPMODE SET TO HIGH


Message text written by DB2 Data Base Discussion List
>
I am having problems with a DB2 CICS transaction the is using 80 % of the
processor. Our CICS
person has all the transaction in the RCT DPMODE set to High. Could this
our transaction to use
so much processor?<

Yes and no. This will allow the transaction to "get" more of the
processor/machine at any point
in time, cpmpared to other jobs/address spaces in the system.
However, if something is using excessive amounts of CPU you need to look at
the application
SQL and access paths.
Additionally, you need to look at the transaction volume, and the amount of
CPU/Tran.
Even efficient transactions can use a lot of total CPU when the volume is
high, and they
are using multiple threads for execution.

Regards,
Joel






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Isaac Yassin

Re: DPMODE SET TO HIGH
(in response to william.poston@DB.COM)
Hi,
If it's pseudo-conversational then each PF7/8 is probably causing another cursor open with
sorting of (probably)
a lot of data and then return the x rows needs for display.
look for the amount of records sorted per each invocation of the transaction - if it's
high, there you have it.
As many people use it extensively - the CPU usage will go up.
Try to look for either a SQL change or maybe add a proper index to reduce the sort.
I guess now is the wrong time in the year to do application changes :-)

Isaac Yassin
[login to unmask email]
----- Original Message -----
From: "William Poston" <[login to unmask email]>
Newsgroups: bit.listserv.db2-l
To: <[login to unmask email]>
Sent: Friday, December 14, 2001 9:04 PM
Subject: Re: DPMODE SET TO HIGH


> Joel I looked at the access path and it looked pretty good except for a sort. Could that
cause the problem?
> The transaction count was very high when this was happening. Apparently because of the
time of year a lot
> of people was using the transaction and the transaction has scrolling (Users can page up
and down on their
> screen) . what do you think?
>
> Thanks
>
>
> ---------------------------------------- Message
History ----------------------------------------
>
>
> From: Joel Goldstein <[login to unmask email]>@RYCI.COM> on 12/14/2001 11:52 AM
EST
>
> Please respond to DB2 Data Base Discussion List <[login to unmask email]>
>
> DELEGATED - Sent by: DB2 Data Base Discussion [login to unmask email]>
>
>
> To: [login to unmask email]
> cc:
> Subject: Re: DPMODE SET TO HIGH
>
>
> Message text written by DB2 Data Base Discussion List
> >
> I am having problems with a DB2 CICS transaction the is using 80 % of the
> processor. Our CICS
> person has all the transaction in the RCT DPMODE set to High. Could this
> our transaction to use
> so much processor?<
>
> Yes and no. This will allow the transaction to "get" more of the
> processor/machine at any point
> in time, cpmpared to other jobs/address spaces in the system.
> However, if something is using excessive amounts of CPU you need to look at
> the application
> SQL and access paths.
> Additionally, you need to look at the transaction volume, and the amount of
> CPU/Tran.
> Even efficient transactions can use a lot of total CPU when the volume is
> high, and they
> are using multiple threads for execution.
>
> Regards,
> Joel
>
>
> DB2-L
webpage at http://www.ryci.com/db2-l. The owners of the list can be reached at
[login to unmask email]
>
>
>
> --
>
> This e-mail may contain confidential and/or privileged information. If you are not the
intended recipient (or have received this e-mail in error) please notify the sender
immediately and destroy this e-mail. Any unauthorized copying, disclosure or distribution
of the material in this e-mail is strictly forbidden.
>
>
> DB2-L
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>



Raymond Bell

Re: DPMODE SET TO HIGH
(in response to Isaac Yassin)
William,

As far as DPMODE is concerned, I'm 90% sure it's only an indication of that
transaction's relative importance, relative to other transactions defined
in the RCT. If they're all define as DPMODE=HIGH then there's no
advantage/disadvantage to any transaction in the RCT.

As to why a transaction would use 80% of your CPU, that's another
question...


Raymond



William Poston
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Sent by: DB2 Subject: Re: DPMODE SET TO HIGH
Data Base
Discussion
List
<[login to unmask email]
M>


15/12/01 04:32
Please respond
to DB2 Data
Base
Discussion
List





I am having problems with a DB2 CICS transaction the is using 80 % of the
processor. Our CICS
person has all the transaction in the RCT DPMODE set to High. Could this
our transaction to use
so much processor?


--

This e-mail may contain confidential and/or privileged information. If you
are not the intended recipient (or have received this e-mail in error)
please notify the sender immediately and destroy this e-mail. Any
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e-mail is strictly forbidden.








James Campbell

Re: DPMODE SET TO HIGH
(in response to Raymond Bell)
Yes, but its importance is higher than CICS. To quote from the
CICS (TS1.1) Performance Guide:

"When DPMODE is specified as HIGH, transactions run at a higher
priority than CICS thus saving virtual storage, releasing locks, and
avoiding other transactions deadlocking or timing out. However, if
all threads are specified with DPMODE HIGH, CICS itself may be
effectively at too low a priority."

and "[i]f the CPU usage per call is high, you should not set
DPMODE=HIGH."


James Campbell



On 17 Dec 2001, at 9:40, Raymond Bell wrote:

Date sent: Mon, 17 Dec 2001 09:40:02 +1300
Send reply to: DB2 Data Base Discussion List <[login to unmask email]>
From: Raymond Bell <[login to unmask email]>
Subject: Re: [DB2-L] DPMODE SET TO HIGH
To: [login to unmask email]

> William,
>
> As far as DPMODE is concerned, I'm 90% sure it's only an indication of that
> transaction's relative importance, relative to other transactions defined
> in the RCT. If they're all define as DPMODE=HIGH then there's no
> advantage/disadvantage to any transaction in the RCT.
>
> As to why a transaction would use 80% of your CPU, that's another
> question...
>
>
> Raymond
>
>
>
> William Poston
> <william.posto To: [login to unmask email]
> [login to unmask email]> cc:
> Sent by: DB2 Subject: Re: DPMODE SET TO HIGH
> Data Base
> Discussion
> List
> <[login to unmask email]
> M>
>
>
> 15/12/01 04:32
> Please respond
> to DB2 Data
> Base
> Discussion
> List
>
>
>
>
>
> I am having problems with a DB2 CICS transaction the is using 80 % of the
> processor. Our CICS
> person has all the transaction in the RCT DPMODE set to High. Could this
> our transaction to use
> so much processor?
>
>
> --

James A Campbell



Raymond Bell

Re: DPMODE SET TO HIGH
(in response to James Campbell)
Hmmm. Did I say 90%? Make that 10%. James, as always, you shoot with
gentle bullets. After firing from the hilt/mouth I did a little DB2
digging. Firstly a definition, from the DB2 V5 Admin Guide, 5.6.4.1
Overview of RCT Options:

DPMODE
Thread TCB priority relative to the CICS main TCB.

Now, the guts. Again the V5 Admin Guide, this time 5.6.4.4 Recommendations
for RCT Definitions:

Setting Thread TCB Priority using DPMODE: The RCT DPMODE parameter controls
the priority of the thread TCBs. In general, specify the default
DPMODE=HIGH for high-priority and high-volume transactions. The purpose is
to execute these transactions quickly, removing them from CICS and DB2.
This helps save virtual storage, and allows the transaction to release its
locks to avoid causing other transactions to deadlock or timeout.

However, if there is a risk that one or more SQL statements in the
transaction will consume a great deal of processor time, allowing the
thread TCB to monopolize the processor, the CICS main TCB might not be
dispatched. (Processor monopolization such as this causes the most impact
on single-CP machines.)

The result of concurrent high priority CICS activity in DB2 can cause
transactions to appear to run longer in DB2. In such cases, CICS tracing
shows the task as "waiting for a DB2 ECB," while the DB2 accounting trace
reports the task as "not in DB2" time. The reason this occurs is that CICS
has not had a chance to dispatch the task that DB2 has posted.

Do not misread this situation and then set DPMODE=HIGH, because the problem
will then get worse. Instead, weigh the importance of the concurrent CICS
activity versus the DB2 activity and adjust the task priorities and the
DPMODE setting accordingly (DPMODE=LOW or DPMODE=EQUAL). With DPMODE=EQUAL,
the thread TCBs actually have an MVS dispatching priority slightly lower
than the CICS main task TCB.

Recommendations for DPMODE: In general, use the following:

DPMODE=HIGH for high-priority and high-volume transactions
DPMODE=EQUAL for transactions that are more CICS-intensive than
DB2-intensive (such as short, simple SQL statements)
DPMODE=LOW for low-priority, short SQL transactions, especially
non-terminal-driven transactions.

What does this mean? That I only got it partly right and omitted (because
I didn't know) the most important bit; that the transactions could run away
with your CPU and deprive CICS of any resource.

Oops.


Raymond
PS. Here (hopefully) endeth the cowboy impersonation/analogy.




James Campbell
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NK.NET.AU> cc:
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17/12/01 13:07
Please respond to
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Yes, but its importance is higher than CICS. To quote from the
CICS (TS1.1) Performance Guide:

"When DPMODE is specified as HIGH, transactions run at a higher
priority than CICS thus saving virtual storage, releasing locks, and
avoiding other transactions deadlocking or timing out. However, if
all threads are specified with DPMODE HIGH, CICS itself may be
effectively at too low a priority."

and "[i]f the CPU usage per call is high, you should not set
DPMODE=HIGH."


James Campbell



On 17 Dec 2001, at 9:40, Raymond Bell wrote:

Date sent: Mon, 17 Dec 2001 09:40:02 +1300
Send reply to: DB2 Data Base Discussion List <[login to unmask email]>
From: Raymond Bell <[login to unmask email]>
Subject: Re: [DB2-L] DPMODE SET TO HIGH
To: [login to unmask email]

> William,
>
> As far as DPMODE is concerned, I'm 90% sure it's only an indication of
that
> transaction's relative importance, relative to other transactions defined
> in the RCT. If they're all define as DPMODE=HIGH then there's no
> advantage/disadvantage to any transaction in the RCT.
>
> As to why a transaction would use 80% of your CPU, that's another
> question...
>
>
> Raymond
>
>
>
> William Poston
> <william.posto To: [login to unmask email]
> [login to unmask email]> cc:
> Sent by: DB2 Subject: Re: DPMODE SET TO
HIGH
> Data Base
> Discussion
> List
> <[login to unmask email]
> M>
>
>
> 15/12/01 04:32
> Please respond
> to DB2 Data
> Base
> Discussion
> List
>
>
>
>
>
> I am having problems with a DB2 CICS transaction the is using 80 % of the
> processor. Our CICS
> person has all the transaction in the RCT DPMODE set to High. Could this
> our transaction to use
> so much processor?
>
>
> --

James A Campbell