Look at the size of my BCHR

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Look at the size of my BCHR

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Tony Davis

Posted Friday, January 09, 2009 12:38 PM

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Comments posted to this topic are about the item Look at the size of my BCHR

Post #633777

Jeff Moden

Posted Friday, January 09, 2009 2:23 PM

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BWAA-HAAA!!! "I'll show you mine if you show me yours."

I've never looked, but I'm just betting that the BCHR is nearly 100% for cursors... ;)

--Jeff Moden

"RBAR is pronounced "ree-bar" and is a "Modenism" for "Row-By-Agonizing-Row".

First step towards the paradigm shift of writing Set Based code:
Stop thinking about what you want to do to a row... think, instead, of what you want to do to a column."

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Post #633892

Michael Valentine Jones

Posted Friday, January 09, 2009 2:55 PM

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I have rarely seen anything below 99%, so I don’t pay much attention to it.

I look more at Average Page Life Expectancy and Page Reads/Sec. These seem to be more volatile and let you know how much thrashing of data pages in and out of memory the server is doing and how much of a bottleneck getting data from disk is.

Post #633923

Steve Jones - SSC Editor

Posted Saturday, January 10, 2009 11:14 AM

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I've honestly stopped checking this at many servers since they're usually > 90%. However I have seen it in the 80s or lower and more memory almost always solves this and gives a little boost.

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Post #634192

george sibbald

Posted Saturday, January 10, 2009 11:32 AM

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well its one of the default performance counters in MOM, which raises a critical alert if it goes below 90% for more than 15 mins (by default) so I guess MS still consider it an indicator of performance.

For myself i admit its nice to see it up high and its something I track as part of memory monitoring but I would only really worry about it if it was ALWAYS low.

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Post #634195

Elisabeth Rédei

Posted Sunday, January 11, 2009 12:50 AM

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Hi,

Since not all memory requests will reflect in the counter you could have > 90% and still have memory issues (and with issues I don't mean low on memory; over consumption is more often the case :P).

But as Steve pointed out, if you encounter a low BCHR and add some memory, there will usually be a performance boost whereas a high number doesn't necessearily mean all is well.

There could be memory issues elsewhere in the bufferpool - anything that goes through the Memory Broker for instance (large memory requests, queries with sort/hash operators, memory for parallel plans etc.) or in the memory area formerly known as mem_to_leave.

I tend to ignore it completely when it's high.

/Elisabeth

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Post #634302

katedgrt

Posted Sunday, January 11, 2009 11:39 AM

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By itself it is not a key indicator, but it can be an important clue if you are having performance issues.

Cool

Kate The Great w00t

If you don't have time to do it right the first time, where will you find time to do it again?

Post #634384

IceDread

Posted Monday, January 12, 2009 1:56 AM

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I dont use it. I measure the time/ workload it takes to perform different tasks that is prio.

Post #634508

GSquared

Posted Monday, January 12, 2009 9:20 AM

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I've never bothered with it. Maybe I should, but I never have.

I've found tracking runtime on queries to be much more useful to me in performance tuning.

- Gus "GSquared", RSVP, OODA, MAP, NMVP, FAQ, SAT, SQL, DNA, RNA, UOI, IOU, AM, PM, AD, BC, BCE, USA, UN, CF, ROFL, LOL, ETC
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Post #634779

Steve Jones - SSC Editor

Posted Monday, January 12, 2009 9:51 AM

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Interesting you've never used it. I use this as a first glance when I get a complaint about a new server. It's a thumb-sketch to see if this is grossly out of whack.

Once I'm familiar with a server, I'd probably never look at it again.

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Post #634805

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