| Page Item | Value |
| Title | Improving ASP Performance With Data Caching |
| Description | Sample VBScript (ASP) code showing how to improve website performance by caching database data |
| Keywords | asp, sql, microsoft access, performance, enhancement, faster |
| Robots Meta Tag | |
| Page Content | ASP Kitchen Search: Go Home | ASP Articles | ASP.NET Articles | Tools | Table Of Contents | What's New Improving ASP Performance With Data Caching One of the nicest features of ASP.NET is the ability to cache page content. This can be used to substantially reduce load on a website's database - which is an obvious attraction if the site uses Microsoft's Access to store data rather than SQL Server. Unfortunately there is no built in caching system in classic ASP, but it is easy to build one by using the Application object to store data. As such the techniques described in this article can be used to bring useful performance enhancements to legacy websites where upgrading the database or porting the code to ASP.NET is not a viable option. An Example of ASP Data Caching In this example, an e-commerce website contains a list of popular products visible in a box displayed on all of the pages within the site. Since the website only takes 2 - 3 orders a day, the list of popular products does not need to be constantly updated. There are three application variables required in the Application_OnStart subroutine of the global.asa file: Application ( CachingDuration ) = 120 Application ( PopularProductsHTML ) = Application ( PopularProductsHTML.LastModified ) = Now () The CachingDuration application variable specifies the number of minutes that the website's cached content should be stored for. The PopularProductsHTML application variable stores the actual HTML for the popular products table. Finally, the PopularProductsHTML.LastModified application variable stores the date and time the popular products HTML was last retrieved from the database. The ASP code for retrieving the popular products from the database is containing within the function GetPopularProductsHTML. There is a single argument - the number of popular products to return: % Function GetPopularProductsHTML (NumberOfProducts) On Error Resume Next Dim DataConnection Dim RecordSet Dim SQL Dim ReturnString Dim ProductName Dim NumberOfProductsDisplayed 'Access Query for returning popular products SQL = sp_GetPopularProducts Set DataConnection = Server.CreateObject ( ADODB.connection ) DataConnection.Open Application ( ConnectionString ) Set RecordSet = Server.CreateObject ( ADODB.Recordset ) RecordSet.Open SQL, DataConnection NumberOfProductsDisplayed = 0 Do While Not RecordSet.EOF If NumberOfProductsDisplayed NumberOfProducts Then ProductName = Replace (RecordSet( ProductName ), Chr(34), ' ) ReturnString = ReturnString a href=ViewProduct.asp?Product= RecordSet( ProductID ) ProductName /a br End If NumberOfProductsDisplayed = NumberOfProductsDisplayed + 1 RecordSet.MoveNext Loop RecordSet.Close Set RecordSet = nothing DataConnection.Close Set DataConnection = nothing GetPopularProductsHTML = ReturnString End Function % This function is called from the ASP VBScript shown below that builds the popular products table. This code also checks that the cached HTML has not expired; if it has expired then the data is retrieved from the database. % Dim PopularProductsBoxTitleText Dim PopularProductsBoxContentsText Dim NumberOfProducts PopularProductsBoxTitleText = Popular Products NumberOfProducts = 25 'If cache is empty then retrieve data from the database If Application ( PopularProductsHTML ) = Then PopularProductsBoxContentsText = GetPopularProductsHTML (NumberOfProducts) Application.Lock () Application ( PopularProductsHTML ) = PopularProductsBoxContentsText Application ( PopularProductsHTML.LastModified ) = Now () Application.UnLock () 'Retrieve content directly from the cache instead of the database Else PopularProductsBoxContentsText = Application ( PopularProductsHTML ) 'Is the cache out of date? If so retrieve the content from the database and store in the cache 'The VBScript DateDiff function can be used to compare dates (n = comparisons of minutes) If DateDiff ( n , Application( PopularProductsHTML.LastModified ), Now()) Application( CachingDuration ) Then Response.Write ( !--Cache Updated-- ) 'Useful debugging line - remove from production code PopularProductsBoxContentsText = GetPopularProductsHTML (NumberOfProducts) 'Store the content in the Application variables. Application.Lock () Application ( PopularProductsHTML ) = PopularProductsBoxContentsText Application ( PopularProductsHTML.LastModified ) = Now () Application.UnLock () End If End If 'Display the popular products box If PopularProductsBoxContentsText Then % div class= BoxOutline div class= BoxTitle span class= PopularProductsBoxTitleText % =PopularProductsBoxTitleText % /span /div div class= BoxContents span class= PopularProductsBoxContentsText % =PopularProductsBoxContentsText % /span /div /div % End If % Don't forget that content stored in Application variables are shared by all users of the site, so if updating Application variables the Lock() method should be called to prevent more than one client from modifying the same Application variable simultaneously. Remember to use the Unlock() method afterwards! When to use ASP Caching Caching is most useful for data that changes - but not too often. For example an e-commerce store could display a list of popular products, or an information site could display a list of press releases. If you have several regions of this information on the same page then the performance increase from caching could be substantial. Don't forget that it is also possible to build functionality into the admin part of the site so that the cache would be flushed if new content is added to the database. That way the website administrator would not have to wait until the cache timed out in order for new content to appear on the website. Remember that data stored in Application variables is visible by all the users of the website, so if your site uses extensive personalisation features you may be better off caching data in the Session object . Links Download the sample source code (4.86 K ZIP file). The ASP syntax highlighting and color coding used in this article was created using the ASP Documentation Tool . Useful Development Tools ASP Documentation Tool Automatically creates developer documentation for ASP 2.0 and 3.0 web applications written in VBScript and JScript. Documentation for Microsoft Access, SQL Server 7/2000 databases and Visual Basic 6.0 components associated with the web application can also be incorporated into the reports. Documentation is created in HTML, HTML Help and plain text formats. View Sample Output (HTML Help format). View Sample Output (HTML Format). Download Trial Version (5.2Mb ZIP file). Index Server Companion The Index Server Companion is a Windows application that extends the functionality of Microsoft Index Server so that it is able to index content from remote websites and also from ODBC databases. As such it can be used as a low cost alternative to Site Server 3.0 Search. View Product Documentation (119K ZIP file). Try Sample Search Facility . Download Trial Version (1.7Mb ZIP file). 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The Website Utility The Website Utility examines websites for errors and areas that need to be optimised for search engines by using a built in web crawling engine. Errors checked for include broken or moved hyperlinks, missing page titles and missing meta tags. It also generates HTML for use in creating website site maps (table of contents pages - like this one ), and is able to create both client-side JavaScript Search Engines and server-side ASP Search Engines for a website. View Sample Output (HTML Format). Download Trial Version (3Mb ZIP file). Text Workbench Text Workbench is a file search and replacement utility for text files and Microsoft Office documents. Make rapid file replacements on multiple files and folders full of files. Advanced replacement options include regular expressions support. It even works on remote file systems via FTP. A Regular Expression Laboratory allows advanced pattern matching and replacement expressions to be built and tested. This great utility will make your everyday development tasks much easier! Download Trial Version (3Mb ZIP file; you have the option to either install directly from this link or save the file for later installation). Author details Brett Burridge spent two years working in the University of Essex Computing Service, before moving to The Internet Applications Group in the Autumn of 1999, where he developed e-Business applications for a range of corporate clients and dot-com start ups. Brett is presently employed as an Internet developer and technical writer through his own company, Winnersh Triangle Web Solutions Limited . The company produces a number of innovative products, including the popular ASP Documentation Tool , the Index Server Companion , the ASP.NET Documentation Tool , the SQL Server Documentation Tool and The Website Utility . The company is also available for web application design and development at reasonable rates, primarily using Microsoft technologies (ASP, ASP.NET, Visual Basic, SQL Server) but also using open source technologies such as PHP, MySQL and Perl. Specialist services include development of search solutions using Microsoft's Index Server and Site Server 3.0 Search. As well as the ASPAlliance, Brett has written articles for Ariadne.ac.uk and ASPToday , and has contributed recipes to the ASP.NET Developer's Cookbook . links Outside web development, Brett is interested in digital photography (here's my photo gallery ), tropical fishkeeping and collecting contemporary works of art by artists such as Doug Hyde . Article history Improving ASP Performance With Data Caching published on ASPAlliance.com on 16 March 2004, last revised 16 March 2004. ASP Kitchen : Classic ASP Articles : Improving ASP Performance With Data Caching
page content copyright Brett Burridge 1998 - 2004. |
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