Re: Informix FAQ
What do you want to know? BTR is an attempt to quantify how much or little churning of the buffer cache is going on. It sums the two IO stats that are primarily incremented by IO that causes a buffer page to be written into (pagreads and bufwrites). That is deivided by the number of buffers in the cache and the hours since the stats were zero'd out to determine how many times the cache has been turned over per hour. This is, of course, an estimate and not particularly accurate. Normally a significant porion of the cache is static - loaded once and never overwritten - so what's really happening is that some subset of the data is being overwritten with new data far more frequently. However, it's the only thing we have that can be reasonably obtained. However, it is still a VERY useful metric. I have determined by observation of many servers that if the BTR is ~10 or under the server is likely happy and users are not complaining about performance. If the BTR is in higher double digits some users will be experiencing slow performance or intermittent responsiveness problems. If BTR is in the upper double or triple digits then your phone is likely ringing with complaints or soon will be. The UBTR was a largely unsuccessful attempt to eliminate unused buffers from the calculation above. However, most production servers do not regularly have any unused buffers. I keep it in the report because it helps to identify a server that has too many buffers configured. Also there are those sites that regularly over configure the cache to contain extra buffers to reduce the impact of periodic complex reporting like end-of-month DSS style queries that require lots more cache. For this last group, if the BTR and UBTR get too close together they want to increase the cache again as the daily working set has grown. Art Art S. Kagel Advanced DataTools (www.advancedatatools.com) IIUG Board of Directors (art@iiug.org) See you at the 2010 IIUG Informix Conference April 25-28, 2010 Overland Park (Kansas City), KS www.iiug.org/conf Disclaimer: Please keep in mind that my own opinions are my own opinions and do not reflect on my employer, Advanced DataTools, the IIUG, nor any other organization with which I am associated either explicitly, implicitly, or by inference. Neither do those opinions reflect those of other individuals affiliated with any entity with which I am affiliated nor those of the entities themselves. On Thu, Jan 7, 2010 at 8:21 AM, Habichtsberg, Reinhard < RHabichtsberg@arz-emmendingen.de> wrote: > Thanks, Art. > > Although I would be happy to search the official FAQ. Seem to me a bit > antiqued but also seem to cover more topic. Actual cause of my search: > Wanted some informations about BTR and so on in reference to your new > ratios_ak. > > Regards, > Reinhard. > > -----Original Message----- > From: informix-list-bounces@iiug.org > [mailto:informix-list-bounces@iiug.org]On Behalf Of Art Kagel > Sent: Thursday, January 07, 2010 12:41 PM > To: Habichtsberg, Reinhard > Cc: Informix-List (E-Mail) > Subject: Re: Informix FAQ > > > Try this one: > > http://www.informixfaq.com/wiki/doku.php > <http://www.informixfaq.com/wiki/doku.php>; > > Art > > Art S. Kagel > AdvanceDataTools ( www.advancedatatools.com > <http://www.advancedatatools.com>; ) > IIUG Board of Directors ( art@iiug.org <mailto:art@iiug.org> ) > > See you at the 2010 IIUG Informix Conference > April 25-28, 2010 > Overland Park (Kansas City), KS > www.iiug.org/conf <http://www.iiug.org/conf>; > > Disclaimer: Please keep in mind that my own opinions are my own opinions > and > do not reflect on my employer, Advanced DataTools, the IIUG, nor any other > organization with which I am associated either explicitly, implicitly, or > by > inference. Neither do those opinions reflect those of other individuals > affiliated with any entity with which I am affiliated nor those of the > entities themselves. > > > > > 2010/1/7 Habichtsberg, Reinhard < RHabichtsberg@arz-emmendingen.de > <mailto:RHabichtsberg@arz-emmendingen.de> > > > > Hi, > > I send this question to the list because the address which is mentioned as > maintainer of the FAQ ( david@smooth1.co.uk <mailto:david@smooth1.co.uk> ) > doesn't work: > > I wanted to search the FAQ as member. Unfortunately the link to search > ( http://www.iiug.org/members/search_faq.html > <http://www.iiug.org/members/search_faq.html>; ) does not work. The result > is > the following message: > > Page Not Found > > Sorry, the page you requested was not found. > > We suggest you try one of the following: > > * Try to find the page you're looking for in the menu. > * Try a keyword search using the Search box above. > * Go to the IIUG home page. > > Is it possible to recover the link? Or do you know any other possibility to > search the FAQ? > > > Kindly regards, > > Reinhard Habichtsberg > DBA > > > Abrechnungszentrum Emmendingen > > An der B3 Haus Nr. 6 > > 79312 Emmendingen > > Tel: 07641 9201-203 > > Fax: 07641 9201-4203 > > E-Mail: rhabichtsberg@arz-emmendingen.de > <mailto:rhabichtsberg@arz-emmendingen.de> > > <<mailto: rhabichtsberg@arz-emmendingen.de > <mailto:rhabichtsberg@arz-emmendingen.de> >> > > < www.arz-emmendingen.de <http://www.arz-emmendingen.de>; >>>>> Auf einen > Blick > > > > Abrechnungszentrum Emmendingen > > Geschäftsführer: Michael Häfele, Stv. Geschäftsführer: Jürgen Ernst > > Eigenbetrieb des BKK Landesverbandes Baden-Württemberg, Körperschaft des > > öffentlichen Rechts, > > vertreten durch den Vorstand > > > > Diese E-Mail und gegebenenfalls ihre Anhänge enthält vertrauliche > und/oder > > rechtlich geschützte, unverbindliche Informationen. Sie ist > ausschließlich > > für den/die darin genannten Empfänger/-in bestimmt. 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