Curiously Low Getpage Requests - V8 for z/OS

Jay Reavill

Curiously Low Getpage Requests - V8 for z/OS
Hello everyone,



Some Omegamon stats have us scratching our heads a bit and we're
wondering if anyone can enlighten us as to why...



We're seeing 150,000 open/close/fetch executions with only 9 total
getpage requests, all of which came from an index (we can tell based on
the BP). The cursors do not require any materialization, used different
predicate values each time, and we suspect that all of them were empty.
However, we would have expected to see at least one getpage per fetch
even if the page was already in the BP. There are thousands of pages on
the index.



Any idea why getpages are so low?



Thanks,

Jay



-------------------------------------------------------------

Jay Reavill

DBA

Fidelity National Information Services, Inc.

11601 Roosevelt Blvd.

St. Petersburg, FL. 33716

Office (727) 227-2144

Mobile (727) 215-5794

[login to unmask email]

-------------------------------------------------------------



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* IDUG 2009 Denver, CO, USA * May 11-15, 2009 * http://IDUG.ORG/Events *
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Robert Catterall

Re: Curiously Low Getpage Requests - V8 for z/OS
(in response to Jay Reavill)
Were these 150,000 open/fetch/close operations associated with one thread
(e.g., a batch job's thread), or with many different threads (e.g., threads
used by CICS-DB2 transactions)?

Robert


On Thu, Jan 22, 2009 at 2:12 PM, Reavill, Jay <[login to unmask email]>wrote:

> Hello everyone,
>
>
>
> Some Omegamon stats have us scratching our heads a bit and we're wondering
> if anyone can enlighten us as to why…
>
>
>
> We're seeing 150,000 open/close/fetch executions with only 9 total getpage
> requests, all of which came from an index (we can tell based on the BP).
> The cursors do not require any materialization, used different predicate
> values each time, and we suspect that all of them were empty. However, we
> would have expected to see at least one getpage per fetch even if the page
> was already in the BP. There are thousands of pages on the index.
>
>
>
> Any idea why getpages are so low?
>
>
>
> Thanks,
>
> Jay
>
>
>
> -------------------------------------------------------------
>
> Jay Reavill
>
> DBA
>
> Fidelity National Information Services, Inc.
>
> 11601 Roosevelt Blvd.
>
> St. Petersburg, FL. 33716
>
> Office (727) 227-2144
>
> Mobile (727) 215-5794
>
> [login to unmask email]
>
> -------------------------------------------------------------
>
>
> _____________
>
> The information contained in this message is proprietary and/or
> confidential. If you are not the
> intended recipient, please: (i) delete the message and all copies; (ii) do
> not disclose,
> distribute or use the message in any manner; and (iii) notify the sender
> immediately. In addition,
> please be aware that any message addressed to our domain is subject to
> archiving and review by
> persons other than the intended recipient. Thank you.
> _____________
>
> ------------------------------
>
> *IDUG 2009 - Australasia * 18-20 March * Melbourne, Australia* < http://idug.org/lsAU >
>
> *IDUG.org* < http://www.idug.org > was recently updated requiring members to
> use a new password. You should have gotten an e-mail with the temporary
> password assigned to your account. Please log in and update your member
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>



--
Robert Catterall
Catterall Consulting
www.catterallconsulting.com

______________________________________________________________________

* IDUG 2009 Denver, CO, USA * May 11-15, 2009 * http://IDUG.ORG/Events *
______________________________________________________________________




IDUG.org was recently updated requiring members to use a new password. You should have gotten an e-mail with the temporary password assigned to your account. Please log in and update your member profile. If you are not already an IDUG.org member, please register at http://www.idug.org/component/juser/register.html

Richard Humphris

Re: Curiously Low Getpage Requests - V8 for z/OS
(in response to Robert Catterall)
Hi Jay,

Perhaps index lookaside is preventing the need to do getpages. I'm
thinking this may be the answer.

See http://www.gabrielledb2.com/iu.pdf for a description of index
lookaside processing.

Rich Humphris


________________________________

From: DB2 Data Base Discussion List [mailto:[login to unmask email]
On Behalf Of Reavill, Jay
Sent: Thursday, January 22, 2009 1:12 PM
To: [login to unmask email]
Subject: [DB2-L] Curiously Low Getpage Requests - V8 for z/OS



Hello everyone,



Some Omegamon stats have us scratching our heads a bit and we're
wondering if anyone can enlighten us as to why...



We're seeing 150,000 open/close/fetch executions with only 9
total getpage requests, all of which came from an index (we can tell
based on the BP). The cursors do not require any materialization, used
different predicate values each time, and we suspect that all of them
were empty. However, we would have expected to see at least one getpage
per fetch even if the page was already in the BP. There are thousands
of pages on the index.



Any idea why getpages are so low?



Thanks,

Jay



-------------------------------------------------------------

Jay Reavill

DBA

Fidelity National Information Services, Inc.

11601 Roosevelt Blvd.

St. Petersburg, FL. 33716

Office (727) 227-2144

Mobile (727) 215-5794

[login to unmask email]

-------------------------------------------------------------



_____________

The information contained in this message is proprietary and/or
confidential. If you are not the
intended recipient, please: (i) delete the message and all
copies; (ii) do not disclose,
distribute or use the message in any manner; and (iii) notify
the sender immediately. In addition,
please be aware that any message addressed to our domain is
subject to archiving and review by
persons other than the intended recipient. Thank you.
_____________


________________________________


IDUG 2009 - Australasia * 18-20 March * Melbourne, Australia
< http://idug.org/lsAU >

IDUG.org < http://www.idug.org > was recently updated requiring
members to use a new password. You should have gotten an e-mail with the
temporary password assigned to your account. Please log in and update
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______________________________________________________________________

* IDUG 2009 Melbourne, Australia * 18-20 March * http://IDUG.ORG/Events *
______________________________________________________________________




IDUG.org was recently updated requiring members to use a new password. You should have gotten an e-mail with the temporary password assigned to your account. Please log in and update your member profile. If you are not already an IDUG.org member, please register at http://www.idug.org/component/juser/register.html

Jay Reavill

Re: Curiously Low Getpage Requests - V8 for z/OS
(in response to Richard Humphris)
Hi Rich,



I think you hit the nail on the head. It's been a long time since I
reviewed what index lookaside actually does and it would appear to make
perfect since in this scenario.



And in answer to Robert's question... This was a single thread batch
program.



Thanks for jogging the old memory cells,

Jay



-------------------------------------------------------------

Jay Reavill

DBA

Fidelity National Information Services, Inc.

11601 Roosevelt Blvd.

St. Petersburg, FL. 33716

Office (727) 227-2144

Mobile (727) 215-5794

[login to unmask email]

-------------------------------------------------------------

________________________________

From: DB2 Data Base Discussion List [mailto:[login to unmask email] On
Behalf Of Humphris,Richard P.
Sent: Friday, January 23, 2009 12:34 AM
To: [login to unmask email]
Subject: Re: [DB2-L] Curiously Low Getpage Requests - V8 for z/OS



Hi Jay,



Perhaps index lookaside is preventing the need to do getpages. I'm
thinking this may be the answer.



See http://www.gabrielledb2.com/iu.pdf for a description of index
lookaside processing.



Rich Humphris


________________________________


From: DB2 Data Base Discussion List [mailto:[login to unmask email]
On Behalf Of Reavill, Jay
Sent: Thursday, January 22, 2009 1:12 PM
To: [login to unmask email]
Subject: [DB2-L] Curiously Low Getpage Requests - V8 for z/OS

Hello everyone,



Some Omegamon stats have us scratching our heads a bit and we're
wondering if anyone can enlighten us as to why...



We're seeing 150,000 open/close/fetch executions with only 9
total getpage requests, all of which came from an index (we can tell
based on the BP). The cursors do not require any materialization, used
different predicate values each time, and we suspect that all of them
were empty. However, we would have expected to see at least one getpage
per fetch even if the page was already in the BP. There are thousands
of pages on the index.



Any idea why getpages are so low?



Thanks,

Jay



-------------------------------------------------------------

Jay Reavill

DBA

Fidelity National Information Services, Inc.

11601 Roosevelt Blvd.

St. Petersburg, FL. 33716

Office (727) 227-2144

Mobile (727) 215-5794

[login to unmask email]

-------------------------------------------------------------



_____________

The information contained in this message is proprietary and/or
confidential. If you are not the
intended recipient, please: (i) delete the message and all
copies; (ii) do not disclose,
distribute or use the message in any manner; and (iii) notify
the sender immediately. In addition,
please be aware that any message addressed to our domain is
subject to archiving and review by
persons other than the intended recipient. Thank you.
_____________




________________________________


IDUG 2009 - Australasia * 18-20 March * Melbourne, Australia
< http://idug.org/lsAU >

IDUG.org < http://www.idug.org > was recently updated requiring
members to use a new password. You should have gotten an e-mail with the
temporary password assigned to your account. Please log in and update
your member profile. If you are not already an IDUG.org member, please
register here. < http://www.idug.org/component/juser/register.html >

E-MAIL CONFIDENTIALITY NOTICE: The contents of this e-mail message and
any attachments are intended solely for the
addressee(s) and may contain confidential and/or legally privileged
information. If you are not the
intended recipient of this message or if this message has been addressed
to you in error, please
immediately alert the sender by reply e-mail and then delete this
message and any attachments. If you
are not the intended recipient, you are notified that any use,
dissemination, distribution, copying, or
storage of this message or any attachment is strictly prohibited.

________________________________


IDUG 2009 - North America * May 11-15 * Denver, Colorado, USA
< http://idug.org/lsna >

IDUG.org < http://www.idug.org > was recently updated requiring members
to use a new password. You should have gotten an e-mail with the
temporary password assigned to your account. Please log in and update
your member profile. If you are not already an IDUG.org member, please
register here. < http://www.idug.org/component/juser/register.html >

_____________

The information contained in this message is proprietary and/or confidential. If you are not the
intended recipient, please: (i) delete the message and all copies; (ii) do not disclose,
distribute or use the message in any manner; and (iii) notify the sender immediately. In addition,
please be aware that any message addressed to our domain is subject to archiving and review by
persons other than the intended recipient. Thank you.
_____________

______________________________________________________________________

* IDUG 2009 Melbourne, Australia * 18-20 March * http://IDUG.ORG/Events *
______________________________________________________________________




IDUG.org was recently updated requiring members to use a new password. You should have gotten an e-mail with the temporary password assigned to your account. Please log in and update your member profile. If you are not already an IDUG.org member, please register at http://www.idug.org/component/juser/register.html

Robert Catterall

Re: Curiously Low Getpage Requests - V8 for z/OS
(in response to Jay Reavill)
Especially since it's a single thread (which is why I asked). I believe
that index lookaside works at a process (e.g., thread) level. In other
words, DB2 could repeatedly access the same index page for a given thread
without additional GETPAGE requests, but I think that this is not the case
for multiple accesses to the same index page from different threads.

Robert


On Fri, Jan 23, 2009 at 8:28 AM, Reavill, Jay <[login to unmask email]>wrote:

> Hi Rich,
>
>
>
> I think you hit the nail on the head. It's been a long time since I
> reviewed what index lookaside actually does and it would appear to make
> perfect since in this scenario.
>
>
>
> And in answer to Robert's question… This was a single thread batch
> program.
>
>
>
> Thanks for jogging the old memory cells,
>
> Jay
>
>
>
> -------------------------------------------------------------
>
> Jay Reavill
>
> DBA
>
> Fidelity National Information Services, Inc.
>
> 11601 Roosevelt Blvd.
>
> St. Petersburg, FL. 33716
>
> Office (727) 227-2144
>
> Mobile (727) 215-5794
>
> [login to unmask email]
>
> -------------------------------------------------------------
> ------------------------------
>
> *From:* DB2 Data Base Discussion List [mailto:[login to unmask email] *On
> Behalf Of *Humphris,Richard P.
> *Sent:* Friday, January 23, 2009 12:34 AM
> *To:* [login to unmask email]
> *Subject:* Re: [DB2-L] Curiously Low Getpage Requests - V8 for z/OS
>
>
>
> Hi Jay,
>
>
>
> Perhaps index lookaside is preventing the need to do getpages. I'm
> thinking this may be the answer.
>
>
>
> See http://www.gabrielledb2.com/iu.pdf for a description of index
> lookaside processing.
>
>
>
> Rich Humphris
>
> ------------------------------
>
> *From:* DB2 Data Base Discussion List [mailto:[login to unmask email] *On
> Behalf Of *Reavill, Jay
> *Sent:* Thursday, January 22, 2009 1:12 PM
> *To:* [login to unmask email]
> *Subject:* [DB2-L] Curiously Low Getpage Requests - V8 for z/OS
>
> Hello everyone,
>
>
>
> Some Omegamon stats have us scratching our heads a bit and we're wondering
> if anyone can enlighten us as to why…
>
>
>
> We're seeing 150,000 open/close/fetch executions with only 9 total getpage
> requests, all of which came from an index (we can tell based on the BP).
> The cursors do not require any materialization, used different predicate
> values each time, and we suspect that all of them were empty. However, we
> would have expected to see at least one getpage per fetch even if the page
> was already in the BP. There are thousands of pages on the index.
>
>
>
> Any idea why getpages are so low?
>
>
>
> Thanks,
>
> Jay
>
>
>
> -------------------------------------------------------------
>
> Jay Reavill
>
> DBA
>
> Fidelity National Information Services, Inc.
>
> 11601 Roosevelt Blvd.
>
> St. Petersburg, FL. 33716
>
> Office (727) 227-2144
>
> Mobile (727) 215-5794
>
> [login to unmask email]
>
> -------------------------------------------------------------
>
>
>
> _____________
>
> The information contained in this message is proprietary and/or
> confidential. If you are not the
> intended recipient, please: (i) delete the message and all copies; (ii) do
> not disclose,
> distribute or use the message in any manner; and (iii) notify the sender
> immediately. In addition,
> please be aware that any message addressed to our domain is subject to
> archiving and review by
> persons other than the intended recipient. Thank you.
> _____________
>
>
> ------------------------------
>
> *IDUG 2009 - Australasia * 18-20 March * Melbourne, Australia* < http://idug.org/lsAU >
> * *
>
> *IDUG.org* < http://www.idug.org > was recently updated requiring members to
> use a new password. You should have gotten an e-mail with the temporary
> password assigned to your account. Please log in and update your member
> profile. If you are not already an IDUG.org member, please register here. < http://www.idug.org/component/juser/register.html >
>
> _____________
>
> The information contained in this message is proprietary and/or
> confidential. If you are not the
> intended recipient, please: (i) delete the message and all copies; (ii) do
> not disclose,
> distribute or use the message in any manner; and (iii) notify the sender
> immediately. In addition,
> please be aware that any message addressed to our domain is subject to
> archiving and review by
> persons other than the intended recipient. Thank you.
> _____________
>
> E-MAIL CONFIDENTIALITY NOTICE: The contents of this e-mail message and any attachments are intended solely for the
> addressee(s) and may contain confidential and/or legally privileged information. If you are not the
> intended recipient of this message or if this message has been addressed to you in error, please
> immediately alert the sender by reply e-mail and then delete this message and any attachments. If you
> are not the intended recipient, you are notified that any use, dissemination, distribution, copying, or
> storage of this message or any attachment is strictly prohibited.
>
>
> ------------------------------
>
> *IDUG 2009 - North America * May 11-15 * Denver, Colorado, USA* < http://idug.org/lsna >
>
> *IDUG.org* < http://www.idug.org > was recently updated requiring members to
> use a new password. You should have gotten an e-mail with the temporary
> password assigned to your account. Please log in and update your member
> profile. If you are not already an IDUG.org member, please register here. < http://www.idug.org/component/juser/register.html >
>
> ------------------------------
>
> *IDUG 2009 - North America * May 11-15 * Denver, Colorado, USA* < http://idug.org/lsna >
>
> *IDUG.org* < http://www.idug.org > was recently updated requiring members to
> use a new password. You should have gotten an e-mail with the temporary
> password assigned to your account. Please log in and update your member
> profile. If you are not already an IDUG.org member, please register here. < http://www.idug.org/component/juser/register.html >
>



--
Robert Catterall
Catterall Consulting
www.catterallconsulting.com

______________________________________________________________________

* IDUG 2009 Melbourne, Australia * 18-20 March * http://IDUG.ORG/Events *
______________________________________________________________________




IDUG.org was recently updated requiring members to use a new password. You should have gotten an e-mail with the temporary password assigned to your account. Please log in and update your member profile. If you are not already an IDUG.org member, please register at http://www.idug.org/component/juser/register.html