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02-27-2008, 02:12 AM
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 victim selection 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      |
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02-27-2008, 02:12 AM
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| Re: victim selection 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 > > |
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02-27-2008, 02:12 AM
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| Re: victim selection 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" <psherman@ameritech.net> wrote in message news  rLid.16381$Rf1.3178@newssvr19.news.prodigy.c om...> From the "Administration Guide: Performance": > The deadlock detector arbitrarily selects one of the applications in the > deadlock and releases the locks currently held by that "volunteered" > application. > > I wouldn't be surprised to see the mechanism used to choose which one > gets cancelled change with a fixpack. This is an internal decision > process that need not be documented beyond what is in the manuals. > > The simplest way to avoid most deadlocks is to establish a shopwide > fixed ordering list for accessing tables. If all applications always > access tables using the same ordering of table access, deadlocks should > be minimized. Designing applications to avoid obtaining locks and > holding them for long periods of time is another major component of > deadlock avoidance. > > > Philip Sherman > > > > Christoph Zeltner wrote: > > Hi, > > > > does anybody know, how victim selection is performed > > within DB2 UDB 8.1if a deadlock occurs ? > > > > One of these ? > > > > a.. current blocker > > a.. youngest XACT > > a.. least resources used > > a.. fewest locks held (common) > > a.. fewest number of restarts > > > > Thx > > Christoph > > > > > |
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02-27-2008, 02:12 AM
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| Re: victim selection I always thought it was "choose the person who will be most affected and most annoyed by being chosen". Your response implies I'm right :-) "Bob [IBM]" <BobAtIBM@canada.com> wrote in message news:2v2r3kF2gjoa1U1@uni-berlin.de... >I could tell you but then I would have to shoot myself > > -- > > Bob > Engagement Specialist - DB2 Information Management Software - IBM Software > Group > IBM Toronto Lab > [My comments are solely my own and are not meant to represent an official > IBM position - > ask my cat!] > "Philip Sherman" <psherman@ameritech.net> wrote in message > news rLid.16381$Rf1.3178@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 >> > >> > >> > > |
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