victim selection

[Christoph Zeltner]

Hi,

does anybody know, how victim selection is performed
within DB2 UDB 8.1if a deadlock occurs ?

One of these ?

a.. current blocker
a.. youngest XACT
a.. least resources used
a.. fewest locks held (common)
a.. fewest number of restarts

Thx
Christoph

[Philip Sherman]

From the "Administration Guide: Performance":
The deadlock detector arbitrarily selects one of the applications in the
deadlock and releases the locks currently held by that "volunteered"
application.

I wouldn't be surprised to see the mechanism used to choose which one
gets cancelled change with a fixpack. This is an internal decision
process that need not be documented beyond what is in the manuals.

The simplest way to avoid most deadlocks is to establish a shopwide
fixed ordering list for accessing tables. If all applications always
access tables using the same ordering of table access, deadlocks should
be minimized. Designing applications to avoid obtaining locks and
holding them for long periods of time is another major component of
deadlock avoidance.
Philip Sherman

Christoph Zeltner wrote:

Hi,

does anybody know, how victim selection is performed
within DB2 UDB 8.1if a deadlock occurs ?

One of these ?

a.. current blocker
a.. youngest XACT
a.. least resources used
a.. fewest locks held (common)
a.. fewest number of restarts

Thx
Christoph

[Bob [IBM]]

I could tell you but then I would have to shoot myself :)

--

Bob
Engagement Specialist - DB2 Information Management Software - IBM Software Group
IBM Toronto Lab
[My comments are solely my own and are not meant to represent an official IBM position -
ask my cat!]
"Philip Sherman" <ps******@ameritech.net> wrote in message
news:or******************@newssvr19.news.prodigy.c om...

From the "Administration Guide: Performance":
The deadlock detector arbitrarily selects one of the applications in the
deadlock and releases the locks currently held by that "volunteered"
application.

I wouldn't be surprised to see the mechanism used to choose which one
gets cancelled change with a fixpack. This is an internal decision
process that need not be documented beyond what is in the manuals.

The simplest way to avoid most deadlocks is to establish a shopwide
fixed ordering list for accessing tables. If all applications always
access tables using the same ordering of table access, deadlocks should
be minimized. Designing applications to avoid obtaining locks and
holding them for long periods of time is another major component of
deadlock avoidance.
Philip Sherman

Christoph Zeltner wrote:

Hi,

does anybody know, how victim selection is performed
within DB2 UDB 8.1if a deadlock occurs ?

One of these ?

a.. current blocker
a.. youngest XACT
a.. least resources used
a.. fewest locks held (common)
a.. fewest number of restarts

Thx
Christoph

[Mark Yudkin]

I always thought it was "choose the person who will be most affected and
most annoyed by being chosen".
Your response implies I'm right :-)

"Bob [IBM]" <Bo******@canada.com> wrote in message
news:2v*************@uni-berlin.de...

I could tell you but then I would have to shoot myself :)

--

Bob
Engagement Specialist - DB2 Information Management Software - IBM Software
Group
IBM Toronto Lab
[My comments are solely my own and are not meant to represent an official
IBM position -
ask my cat!]
"Philip Sherman" <ps******@ameritech.net> wrote in message
news:or******************@newssvr19.news.prodigy.c om...

From the "Administration Guide: Performance":
The deadlock detector arbitrarily selects one of the applications in the
deadlock and releases the locks currently held by that "volunteered"
application.

I wouldn't be surprised to see the mechanism used to choose which one
gets cancelled change with a fixpack. This is an internal decision
process that need not be documented beyond what is in the manuals.

The simplest way to avoid most deadlocks is to establish a shopwide
fixed ordering list for accessing tables. If all applications always
access tables using the same ordering of table access, deadlocks should
be minimized. Designing applications to avoid obtaining locks and
holding them for long periods of time is another major component of
deadlock avoidance.
Philip Sherman

Christoph Zeltner wrote:

> Hi,
>
> does anybody know, how victim selection is performed
> within DB2 UDB 8.1if a deadlock occurs ?
>
> One of these ?
>
> a.. current blocker
> a.. youngest XACT
> a.. least resources used
> a.. fewest locks held (common)
> a.. fewest number of restarts
>
> Thx
> Christoph
>
>