Help on Slow System

Wayne Stevens

Help on Slow System
We just added 72 partitions to a tablespace bringing the total to 200
from 128. We rebound all the packages that were tied to the TS with
REBIND. We did an compare of the access paths before and after and
there were no changes. CICS transactions brought the system to a
standstill. We brought down CICS and everything else is running fine
now.



Wayne Stevens

334-353-7482

888-535-1552 Cell

888-535-1554 FAX

[login to unmask email] <mailto:[login to unmask email]>






______________________________________________________________________

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



The IDUG DB2-L Listserv is only part of your membership in IDUG. The DB2-L list archives, FAQ, and delivery preferences are at http://www.idug.org/lsidug under the Listserv tab. While at the site, you can also access the IDUG Online Learning Center, Tech Library and Code Place, see the latest IDUG conference information and much more. If you have not yet signed up for Basic Membership in IDUG, available at no cost, click on Member Services at http://www.idug.org/lsms

Isaac Yassin

Re: Help on Slow System
(in response to Wayne Stevens)
TCBLIMIT({12|value})



Specifies the maximum number of TCBs that can be used to process DB2 requests. The default is 12. The minimum number is 4 and the maximum is 2000. When connected to DB2

Version 5 or earlier, the CICS DB2 attachment facility creates the TCBs in the form of subtasks up to the limit specified by TCBLIMIT. Each of these subtasks identifies to DB2 and

creates a connection into DB2. When connected to DB2 Version 6 or later, CICS creates open TCBs (up to the limit specified by the system initialization parameter MAXOPENTCBS).

The TCBLIMIT attribute of the DB2CONN definition governs how many of the open TCBs can be used to access DB2 -- that is, how many of them can identify to DB2 and create a

connection into DB2.



The TCBLIMIT value controls the total number of threads for the CICS region. For this reason, the recommended value for TCBLIMIT is the sum of all the thread limit values (that is, the

sum of all THREADLIMIT attributes on the DB2 connection and DB2 entry resource definitions, plus the COMTHREADLIMIT value on the DB2 connection definition) up to the limit of 2000.



When CICS is connected to DB2 Version 5 or earlier, note that if you specify THREADLIMIT values which, in total, exceed the number of TCBs (TCBLIMIT) that can be created, a

task could acquire a thread and then find that there is no available TCB. In this case, the task is suspended, with the INQUIRE TASK command showing HTYPE(CDB2TCB) with no

corresponding HVALUE. This contrasts with the case where a task is suspended waiting for a thread, which shows HTYPE(CDB2RDYQ) and HVALUE(*POOL), HVALUE(*COMD), or

HVALUE(entry_name), as appropriate.



When CICS is connected to DB2 Version 6 or later, note that if MAXOPENTCBs is exceeded (so no more open TCBs can be created), the task is suspended with

HTYPE(DISPATCH) and HVALUE(OPEN_TCB). If MAXOPENTCBs is not exceeded but TCBLIMIT is exceeded , then the task is suspended with HTYPE(CDB2CONN). In this situation,

although CICS has an open TCB available, the maximum allowed number of open TCBs are being used to access DB2 (as defined in TCBLIMIT).



When determining the number for TCBLIMIT, you must consider the amount you specified for the MAX USERS parameter on DB2 installation panel DSNTIPE.



Isaac Yassin

From: DB2 Data Base Discussion List [mailto:[login to unmask email] On Behalf Of Stevens, Wayne
Sent: Monday, December 15, 2008 6:32 PM
To: [login to unmask email]
Subject: [DB2-L] Help on Slow System



We just added 72 partitions to a tablespace bringing the total to 200 from 128. We rebound all the packages that were tied to the TS with REBIND. We did an compare of the access paths before and after and there were no changes. CICS transactions brought the system to a standstill. We brought down CICS and everything else is running fine now.



Wayne Stevens

334-353-7482

888-535-1552 Cell

888-535-1554 FAX

<mailto:[login to unmask email]> [login to unmask email]







_____

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

The IDUG DB2-L Listserv is only part of your membership in IDUG. The DB2-L list archives, FAQ, and delivery preferences are at IDUG.ORG <http://www.idug.org/lsidug> under the Listserv tab. While at the site, you can also access the IDUG Online Learning Center, Tech Library and Code Place, see the latest IDUG conference information <http://www.idug.org/lsconf> , and much more. If you have not yet signed up for Basic Membership in IDUG, available at no cost, click on Member Services < http://www.idug.org/lsms >


______________________________________________________________________

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



The IDUG DB2-L Listserv is only part of your membership in IDUG. The DB2-L list archives, FAQ, and delivery preferences are at http://www.idug.org/lsidug under the Listserv tab. While at the site, you can also access the IDUG Online Learning Center, Tech Library and Code Place, see the latest IDUG conference information and much more. If you have not yet signed up for Basic Membership in IDUG, available at no cost, click on Member Services at http://www.idug.org/lsms

Larry Kintisch

Re: Help on Slow System
(in response to Isaac Yassin)
Hi Isaac,
For those of us like me who are not systems folks [nor CICS
specialists] it would help if you explained why the TCB count
increased when the number of partitions increased. Thanks, Larry
Kintisch ABLE Information Services

At 12:06 PM 12/15/2008, you wrote:
>TCBLIMIT({12|value})
>
> Specifies the maximum number of TCBs that can be used to
> process DB2 requests. The default is 12. The minimum number is 4
> and the maximum is 2000. When connected to DB2
> Version 5 or earlier, the CICS DB2 attachment facility creates
> the TCBs in the form of subtasks up to the limit specified by
> TCBLIMIT. Each of these subtasks identifies to DB2 and
> creates a connection into DB2. When connected to DB2 Version 6
> or later, CICS creates open TCBs (up to the limit specified by the
> system initialization parameter MAXOPENTCBS).
> The TCBLIMIT attribute of the DB2CONN definition governs how
> many of the open TCBs can be used to access DB2 -- that is, how
> many of them can identify to DB2 and create a
> connection into DB2.
>
> The TCBLIMIT value controls the total number of threads for the
> CICS region. For this reason, the recommended value for TCBLIMIT is
> the sum of all the thread limit values (that is, the
> sum of all THREADLIMIT attributes on the DB2 connection and DB2
> entry resource definitions, plus the COMTHREADLIMIT value on the
> DB2 connection definition) up to the limit of 2000.
>
> When CICS is connected to DB2 Version 5 or earlier, note that
> if you specify THREADLIMIT values which, in total, exceed the
> number of TCBs (TCBLIMIT) that can be created, a
> task could acquire a thread and then find that there is no
> available TCB. In this case, the task is suspended, with the
> INQUIRE TASK command showing HTYPE(CDB2TCB) with no
> corresponding HVALUE. This contrasts with the case where a task
> is suspended waiting for a thread, which shows HTYPE(CDB2RDYQ) and
> HVALUE(*POOL), HVALUE(*COMD), or
> HVALUE(entry_name), as appropriate.
>
> When CICS is connected to DB2 Version 6 or later, note that if
> MAXOPENTCBs is exceeded (so no more open TCBs can be created), the
> task is suspended with
> HTYPE(DISPATCH) and HVALUE(OPEN_TCB). If MAXOPENTCBs is not
> exceeded but TCBLIMIT is exceeded , then the task is suspended with
> HTYPE(CDB2CONN). In this situation,
> although CICS has an open TCB available, the maximum allowed
> number of open TCBs are being used to access DB2 (as defined in TCBLIMIT).
>
> When determining the number for TCBLIMIT, you must consider the
> amount you specified for the MAX USERS parameter on DB2
> installation panel DSNTIPE.
>
>Isaac Yassin
>From: DB2 Data Base Discussion List [mailto:[login to unmask email] On
>Behalf Of Stevens, Wayne
>Sent: Monday, December 15, 2008 6:32 PM
>To: [login to unmask email]
>Subject: [DB2-L] Help on Slow System
>
>We just added 72 partitions to a tablespace bringing the total to
>200 from 128. We rebound all the packages that were tied to the TS
>with REBIND. We did an compare of the access paths before and after
>and there were no changes. CICS transactions brought the system to
>a standstill. We brought down CICS and everything else is running fine now.
>
>Wayne Stevens
>334-353-7482
>888-535-1552 Cell
>888-535-1554 FAX
><mailto:[login to unmask email]>[login to unmask email]
>
>
>
>
> < http://idug.org/lsNA > IDUG 2009 - North America * May 11-15, 2009 *
>Denver, CO, USA
>
>The IDUG DB2-L Listserv is only part of your membership in IDUG. The
>DB2-L list archives, FAQ, and delivery preferences are at
> < http://www.idug.org/lsidug > IDUG.ORG under the Listserv tab. While
>at the site, you can also access the IDUG Online Learning Center,
>Tech Library and Code Place, see the latest IDUG
> < http://www.idug.org/lsconf > conference information, and much more.
>If you have not yet signed up for Basic Membership in IDUG,
>available at no cost, click on < http://www.idug.org/lsms > Member Services
>
>
> < http://idug.org/lsNA > IDUG 2009 - North America * May 11-15, 2009 *
>Denver, CO, USA
>
>The IDUG DB2-L Listserv is only part of your membership in IDUG. The
>DB2-L list archives, FAQ, and delivery preferences are at
> < http://www.idug.org/lsidug > IDUG.ORG under the Listserv tab. While
>at the site, you can also access the IDUG Online Learning Center,
>Tech Library and Code Place, see the latest IDUG
> < http://www.idug.org/lsconf > conference information, and much more.
>If you have not yet signed up for Basic Membership in IDUG,
>available at no cost, click on < http://www.idug.org/lsms > Member Services

______________________________________________________________________

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



The IDUG DB2-L Listserv is only part of your membership in IDUG. The DB2-L list archives, FAQ, and delivery preferences are at http://www.idug.org/lsidug under the Listserv tab. While at the site, you can also access the IDUG Online Learning Center, Tech Library and Code Place, see the latest IDUG conference information and much more. If you have not yet signed up for Basic Membership in IDUG, available at no cost, click on Member Services at http://www.idug.org/lsms

M. Khalid Khan

Re: Help on Slow System
(in response to Larry Kintisch)
If cics transactions can't get through to db2 for the lack of
threads/tcbs, these transactions will hang/abend with no adverse effect
other work. But the description of the problem "brought the system to a
standstill" tells that it's not the case, rather some cics transactions
are using up so much resources as to cause a system wide slowdown.
Unfortunately the information provided is too little for any specific
comment. Generically I'd suggest the isolation of the
transactions/packages hogging the resources and proceed from there.
Khalid




Hi Isaac,
For those of us like me who are not systems folks [nor CICS
specialists] it would help if you explained why the TCB count
increased when the number of partitions increased. Thanks, Larry
Kintisch ABLE Information Services

At 12:06 PM 12/15/2008, you wrote:
>TCBLIMIT({12|value})
>
> Specifies the maximum number of TCBs that can be used to
> process DB2 requests. The default is 12. The minimum number is 4
> and the maximum is 2000. When connected to DB2
> Version 5 or earlier, the CICS DB2 attachment facility creates
> the TCBs in the form of subtasks up to the limit specified by
> TCBLIMIT. Each of these subtasks identifies to DB2 and
> creates a connection into DB2. When connected to DB2 Version 6
> or later, CICS creates open TCBs (up to the limit specified by the
> system initialization parameter MAXOPENTCBS).
> The TCBLIMIT attribute of the DB2CONN definition governs how
> many of the open TCBs can be used to access DB2 -- that is, how
> many of them can identify to DB2 and create a
> connection into DB2.
>
> The TCBLIMIT value controls the total number of threads for the
> CICS region. For this reason, the recommended value for TCBLIMIT is
> the sum of all the thread limit values (that is, the
> sum of all THREADLIMIT attributes on the DB2 connection and DB2
> entry resource definitions, plus the COMTHREADLIMIT value on the
> DB2 connection definition) up to the limit of 2000.
>
> When CICS is connected to DB2 Version 5 or earlier, note that
> if you specify THREADLIMIT values which, in total, exceed the
> number of TCBs (TCBLIMIT) that can be created, a
> task could acquire a thread and then find that there is no
> available TCB. In this case, the task is suspended, with the
> INQUIRE TASK command showing HTYPE(CDB2TCB) with no
> corresponding HVALUE. This contrasts with the case where a task
> is suspended waiting for a thread, which shows HTYPE(CDB2RDYQ) and
> HVALUE(*POOL), HVALUE(*COMD), or
> HVALUE(entry_name), as appropriate.
>
> When CICS is connected to DB2 Version 6 or later, note that if
> MAXOPENTCBs is exceeded (so no more open TCBs can be created), the
> task is suspended with
> HTYPE(DISPATCH) and HVALUE(OPEN_TCB). If MAXOPENTCBs is not
> exceeded but TCBLIMIT is exceeded , then the task is suspended with
> HTYPE(CDB2CONN). In this situation,
> although CICS has an open TCB available, the maximum allowed
> number of open TCBs are being used to access DB2 (as defined in
TCBLIMIT).
>
> When determining the number for TCBLIMIT, you must consider the
> amount you specified for the MAX USERS parameter on DB2
> installation panel DSNTIPE.
>
>Isaac Yassin
>From: DB2 Data Base Discussion List [mailto:[login to unmask email] On
>Behalf Of Stevens, Wayne
>Sent: Monday, December 15, 2008 6:32 PM
>To: [login to unmask email]
>Subject: [DB2-L] Help on Slow System
>
>We just added 72 partitions to a tablespace bringing the total to
>200 from 128. We rebound all the packages that were tied to the TS
>with REBIND. We did an compare of the access paths before and after
>and there were no changes. CICS transactions brought the system to
>a standstill. We brought down CICS and everything else is running fine
now.
>
>Wayne Stevens



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______________________________________________________________________

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



The IDUG DB2-L Listserv is only part of your membership in IDUG. The DB2-L list archives, FAQ, and delivery preferences are at http://www.idug.org/lsidug under the Listserv tab. While at the site, you can also access the IDUG Online Learning Center, Tech Library and Code Place, see the latest IDUG conference information and much more. If you have not yet signed up for Basic Membership in IDUG, available at no cost, click on Member Services at http://www.idug.org/lsms