[This is preliminary documentation and subject to change]

# Caching Applications

By adjusting several settings associated with Web applications that run on your server, you can fine-tune server performance. Logging usage data, such as number of requests and the time they were made, can help you determine how to make the adjustments. For more information on logging server activity, see Logging Site Activity. For additional information on performance issues, see About Performance Tuning.

The following settings are covered:

- Setting the CGI Script Timeout
- Caching ISAPI extensions
- Caching ASP Script Files

## Setting the CGI Script Timeout

In addition to the timeout associated with the connection, you can set a timeout value for CGI scripts. The timeout value is the amount of time a CGI script is given to execute. CGI applications inherit the timeout setting for the entire Web site. You can change the setting for the entire Web site or for an isolated application.

To set the timeout value:

1. In the IIS snap-in, select the Computer icon, and open its property sheets.
2. Under Master Properties, select WWW Service, and click the Edit button.
3. Click the Home Directory tab.
4. Click the Configuration button.
5. Click the Process Options Property Sheet tab, and type the timeout period in the CGI Script Timeout text box.

## Caching ISAPI extensions

ISAPI DLLs can be loaded and cached so that further requests can be processed without calling them again. Otherwise, the DLLs are unloaded after they are run. Caching reduces the time a user waits for a DLL to load and most ISAPI extensions (including Active Server Pages) benefit from caching. You should clear this option only for special circumstances, such as debugging ISAPI extensions.

###### To enable caching:

1. In the IIS snap-in, select the Web site or the starting point directory of an application.
2. Open the directory's property sheets, and click the Home Directory, Virtual Directory, or Directory tab.
3. Click the Configuration button.
4. On the Mappings tab, select the Cache ISAPI extensions check box.

## Caching ASP Script Files

ASP processes the files containing ASP scripts, stores these processed files in a cache, and serves the cached files to clients. Caching ASP files enhances performance because cached ASP scripts are not processed each time they are called. You can further improve performance by changing the number of cached files for all applications with low (in process) or medium (pooled) protection, or individually for applications with high (isolated) application protection.

To change the settings for caching ASP files:

1. In the IIS snap-in, select the desired Web site, virtual directory, or directory, and select its property pages.
2. Click the Home Directory tab for a Web site, the Virtual Directorytab a virtual directory, or the Directory tab for a directory.
3. In the Application Settings section, set Application Protection to High (Isolated), and click Apply.
4. Click the Configuration button.

   Note If the Configuration button is not active, the directory or starting point does not contain an isolated application. You can create a new application by clicking the Create button.

5. Click the Cache Options tab.
6. To cache all requested .asp files, select Cache all requested ASP files. To set the maximum number of files cached in memory, type a value in the text box (files in excess of this number are persisted to the disk cache).
7. To limit the total number of ASP files cached, select Limit ASP files cached to:, and enter a value in the text box.
8. To turn off the cache, select Do not cache ASP files.

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