Tips for improving performance and styling 25+ ASP techniques
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Len Cardinal-microsoft Consulting Services Senior Advisor
George v. Reilly-microsoft, IIS performance supervisor
Update Time: April 2000
According to Nancy Cluts's article (English) rewrite
Nancy Cluts-Developer technical engineer
Microsoft Corporation
Summary: This article provides tips for optimizing ASP applications and VBScript.
Directory
Brief introduction
Tip 1: Caching common data on a WEB server
Tip 2: Cache commonly used data in application or session objects
Tip 3: Caching Data and HTML on a WEB server disk
Tip 4: Avoid caching inflexible components in application or Session objects
Tip 5: Do not cache a database connection in a application or Session object
Tip 6: Magical Session Objects
Tip 7: Encapsulate code in a COM object
Tip 8: Get resources later and release resources early
Tip 9: Out-of-process execution will sacrifice reliability
Tip 10: Explicit Use options
Tip 11: Use local variables in subroutines and functions
Tip 12: Copy common data to a script variable
Tip 13: Avoid redefining arrays
Tip 14: Use response buffering
Tip 15: Batch inline scripts and Response.Write statements
Tip 16: Use response.isclientconnected before you start a long task
Tip 17: Instantiate objects with <OBJECT> tags
Tip 18: Use the TypeLib binding of ADO objects and other components
Tip 19: Leverage your browser's ability to authenticate
Tip 20: Avoid string concatenation in loops
Tip 21: Enable browser and proxy caching
Tip 22: Use Server.Transfer instead of Response.Redirect whenever possible
Tip 23: Add a slash at the end of the directory URL
Tip 24: Avoid using server variables
Tip 25: Upgrade to the latest and best version
Tip 26: Adjust your WEB server
Tip 27: Perform a performance test
Tip 28: Read Resource Links
Brief introduction
Performance is an attribute. You need to design your performance in advance, or rewrite your application later. In other words, what is a good strategy for maximizing the performance of Active Server Pages (ASP) applications?
This article provides a number of tips for optimizing ASP applications and the Visual Basic (R) Script Editor (VBScript). Many pitfalls and flaws were discussed. The recommendations listed in this article have been tested on http://www.microsoft.com and other sites and are working properly. This article assumes that you have a basic understanding of ASP development, including for VBScript and/or JScript, ASP application, ASP sessions, and other ASP internal objects (requests, responses, and servers).
ASP's performance, usually depends not only on the ASP code itself. We do not want to include all the wisdom in an article, but only at the end of the list of resources related to performance. These links include ASP and non-ASP topics, including ActiveX (R) Data Objects (ADO), part object Model (COM), databases, and Internet Information Server (IIS) configurations. These are our favorite links-be aware of them.
Tip 1: Caching common data on a WEB server
A typical ASP page retrieves data from the back-end database and then converts the result to Hypertext Markup Language (HTML). Retrieving data from memory is much faster than retrieving data from a back-end database, regardless of the speed of the database. Reading data from a local hard disk is often much faster than retrieving data from a database. As a result, you can often improve performance by caching data on a WEB server (in memory or disk).
Caching is a typical tradeoff between space and time. If you cache the data appropriately, you will see a dramatic improvement in performance. To make the cache work, it must maintain data that is frequently reused, and the cost of recalculation of the data is expensive or more expensive. If the cache is full of garbage data, it is a waste of memory.
Data that is infrequently changed is also a cached candidate because you do not have to worry about synchronizing data with the database. combo boxes, reference tables, DHTML fragments, Extensible Markup Language (XML) strings, menu items, and site configuration variables, including data source names (DSNs), Internet Protocol (IP) addresses, and Web paths) are cached candidate data. Note that you can cache the representation of the data rather than the data itself. If ASP pages do not change frequently and the cost of caching is very high (for example, the entire product catalog), consider generating HTML beforehand, rather than redrawing each request.
Where should the data be cached, and what caching policies are there? Data is often cached on Web server memory or on a Web server disk. The following two tips discuss these options.
Tip 2: Cache commonly used data in application or session objects
ASP Application and Session objects provide a convenient container for caching data in memory. You can either give the data to the Application object or assign the data to the session object, which will remain in memory in the HTTP call. Session data is stored by user, and application data is shared among all users.
When will data be loaded into application or session? Typically, the data is loaded when the application or session is started. To load data at application or session startup, add the appropriate code in the following two functions: Application_OnStart () or Session_OnStart (). These two functions should be in Global.asa, and if not, you can add these functions. You can also load data the first time you need it. To do this, add some code (or write reusable script functions) to the ASP page that checks for the existence of the data and loads the data when it does not exist. This is an example of a classical energy technique called lazy Computing-no calculation before you really need it. Take a look at the example:
<%
Function getemploymentstatuslist
Dim D
D = Application ("Employmentstatuslist")
If d = "" Then
' Fetchemploymentstatuslist function (not shown)
' Fetch data from DB, return array
D = fetchemploymentstatuslist ()
Application ("employmentstatuslist") = d
End If
Getemploymentstatuslist = d
End Function
%>
You can write similar functions for each piece of data that you want.
What format should the data be stored in? Any variable type can be stored, because all script variables are different. For example, you can store strings, integers, or arrays. Typically, you will store the contents of an ADO recordset as one of these variable types. To get data derived from an ADO recordset, you can manually copy the data into a VBScript variable, one field at a time. Using an ADO recordset to preserve Functions GetRows (), GetString (), or Save () (ADO 2.5) is faster and easier. The full and detailed content is beyond the scope of this article. The following demo function uses GetRows () to return an array of recordset data:
' Fetch Recordset, return with array
Function fetchemploymentstatuslist
Dim RS
Set rs = CreateObject ("ADODB.") Recordset ")
Rs. Open "Select Statusname, Statusid from Employeestatus", _
"Dsn=employees;uid=sa;pwd=;"
Fetchemploymentstatuslist = Rs. GetRows () ' Returns data as an array
Rs. Close
Set rs = Nothing
End Function
Further improvements to the above example should be to cache the HTML of the list, rather than caching the array. The following is a simple example:
' Take the recordset and return it in the HTML options list
Function fetchemploymentstatuslist
Dim RS, Fldname, S
Set rs = CreateObject ("ADODB.") Recordset ")
Rs. Open "Select Statusname, Statusid from Employeestatus", _
"Dsn=employees;uid=sa;pwd=;"
s = "<select name=" "Employmentstatus" > "& vbCrLf
Set fldname = Rs. Fields ("Statusname") ' ADO field bindings
Do Until Rs. Eof
' Under
