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# calculate package cache hit ratio

 P: n/a the formula for package cache hit ratio is 1 - (package cache inserts/package cache lookups), what the result would be a effective ratio? currently we have cache inserts=25, cache lookups=35, so i get ratio =0.28, is this a good number? Nov 12 '05 #1
4 Replies

 P: n/a No it is not. The formula can be used as: (1 -Inserts/Lookups) * 100 In your case, you get 28.57%. You aim is to get => 80% Be careful. If the cache is empty, you'll obviously get a low ratio. You should snapshot when the db has been activated, users have logged on and have started using their application. Normally a low ratio is an indication of a Package Cache too small. HTH, Pierre xixi wrote: the formula for package cache hit ratio is 1 - (package cache inserts/package cache lookups), what the result would be a effective ratio? currently we have cache inserts=25, cache lookups=35, so i get ratio =0.28, is this a good number? -- Pierre Saint-Jacques - Reply to: sesconsjunk at attglobaljunk dot com Reconstruct address: Remove the two junk and replace at and dot by their symbols. IBM DB2 Cerified Solutions Expert - Administration SES Consultants Inc. Nov 12 '05 #2

 P: n/a No it is not. The formula can be used as: (1 -Inserts/Lookups) * 100 In your case, you get 28.57%. You aim is to get => 80% Be careful. If the cache is empty, you'll obviously get a low ratio. You should snapshot when the db has been activated, users have logged on and have started using their application. Normally a low ratio is an indication of a Package Cache too small. HTH, Pierre xixi wrote: the formula for package cache hit ratio is 1 - (package cache inserts/package cache lookups), what the result would be a effective ratio? currently we have cache inserts=25, cache lookups=35, so i get ratio =0.28, is this a good number? -- Pierre Saint-Jacques - Reply to: sesconsjunk at attglobaljunk dot com Reconstruct address: Remove the two junk and replace at and dot by their symbols. IBM DB2 Cerified Solutions Expert - Administration SES Consultants Inc. Nov 12 '05 #3

 P: n/a Not really - but on the other hand your sample is so small that it's not particularly meaningful. I have these values: Package cache lookups = 6368651 Package cache inserts = 396292 which comes out to around .94. I'd suggest you hammer your database for a while before taking the snapshot so you get a better feel for what's going on under load. The packages are cached (inserted) the first time they're used, and the next time they're needed they will be retrieved from the cache if they're still there (lookup). /T da****@yahoo.com (xixi) wrote in message news:... the formula for package cache hit ratio is 1 - (package cache inserts/package cache lookups), what the result would be a effective ratio? currently we have cache inserts=25, cache lookups=35, so i get ratio =0.28, is this a good number? Nov 12 '05 #4

 P: n/a Not really - but on the other hand your sample is so small that it's not particularly meaningful. I have these values: Package cache lookups = 6368651 Package cache inserts = 396292 which comes out to around .94. I'd suggest you hammer your database for a while before taking the snapshot so you get a better feel for what's going on under load. The packages are cached (inserted) the first time they're used, and the next time they're needed they will be retrieved from the cache if they're still there (lookup). /T da****@yahoo.com (xixi) wrote in message news:... the formula for package cache hit ratio is 1 - (package cache inserts/package cache lookups), what the result would be a effective ratio? currently we have cache inserts=25, cache lookups=35, so i get ratio =0.28, is this a good number? Nov 12 '05 #5

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