Re: Application Server Caching

Ryan,

Our application does a certain amount of application server caching, and infact has a pretty advanced cache mechanism to deal with out of date objects, etc.
On a more simple level - Common reference records are loaded at start up and cached, error messages are cached, etc. In a similar fashion we a a sequence providing GUID values (global across our application at least) - Obviously the application chews through these very fast (millions per day). So, to reduce load each time the application gets a new value from the sequence it treats it as a range of 1000 values. If the app crashes we only loose a few thousand sequence numbers (several processes each have their own store of 1000 values) but access to the sequence is reduced by a factor of 1000. After three years of running the sequence is around 10,000,000 instead of 10,000,000,000!

It's all a matter of knowing what to cache and how to ensure it's still current. If you were populating a list of State Codes for a drop down list then I would cache that result but something like a StockOnHandQuantity figure probably changes so often that caching is of little use.

If you have the same query (ficticious eg: select statename, statecode from states) constantly firing in your database then I guess it's a sign that caching would help. Even sub-second queries can quickly add up in a busy system.

Cheers,

      Mark.

                                                                                                                                      
                      "Ryan"                                                                                                          
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                      ml-errors_at_fatcity                                                                                               
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                      15/01/2004 09:14                                                                                                
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I heard a presentation from a front end performance analyst last night from www.tangasol.com (im not associated with them at all). He was pretty impressive.

He argued that accessing the database is expensive. He also argued in favor of caching data at the application server level. Have any of you worked with this? What are your opinions? His opinion was that people go back to the database to ask the same question way too often and cause a botteneck, if you can cache these frequently asked questions at the front end, it will significantly scale better.

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Author: Mark Richard
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