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See how to read. The content you requested has been removed. Ask a question. Quick access. Search related threads. Remove From My Forums. Asked by:. Archived Forums. NET Managed Providers. NET managed providers, especially System. SqlClient, System. The Command object's Parameters collection saves you the trouble of reconstructing your query each time you want to reissue your query. For example, if you need to regularly update supply and cost information in your Web-based inventory system, you can predefine your query in the following way:.
ADO parameters, such as adCmdText , are simply variables, this means that before using an ADO parameter in a data access script you need to define its value. Since ADO uses a large number of parameters, it is easier to define parameters by means of a component type library, a file containing definitions for every ADO parameter and constant.
In the previous example, you will note that the script repeatedly constructs and reissues a SQL query with different values, without having to redefine and resend the query to the database source. Compiling your queries with the Command object also offers you the advantage of avoiding problems that can arise from concatenating strings and variables to form SQL queries.
In particular, by using the Command object's Parameter collection, you can avoid problems related to defining certain types of string, date, and time variables. For example, SQL query values containing apostrophes ' can cause a query to fail:. By binding the query value as a Command object parameter, you avoid this type of problem. Web pages containing HTML forms can enable users to remotely query a database and retrieve specific information.
With ADO you can create surprisingly simple scripts that collect user form information, create a custom database query, and return information to the user. For example, the following script block inserts information supplied by an HTML form into a table. The script collects the user information with the Request object 's Form collection.
One of the main challenges of designing a sophisticated Web database application, such as an online order entry application that services thousands of customers, is properly managing database connections.
Opening and maintaining database connections, even when no information is being transmitted, can severely strain a database server's resources and result in connectivity problems. Well designed Web database applications recycle database connections and compensate for delays due to network traffic. A database server experiencing a sudden increase in activity can become backlogged, greatly increasing the time required to establish a database connection. As a result, excessive connection delays can reduce the performance of your database application.
With the Connection object's ConnectionTimeout you can limit the amount of time that your application waits before abandoning a connection attempt and issuing an error message. For example, the following script sets the ConnectionTimeout property to wait twenty seconds before cancelling the connection attempt:.
Before incorporating the ConnectionTimeout property into your database applications, make sure that your connection provider and data source support this property. Connection pooling enables your Web application to use a connection from a pool, or reservoir of free connections that do not need to be reestablished.
After a connection has been created and placed in a pool, your application reuses that connection without having to perform the connection process. This can result in significant performance gains, especially if your application connects over a network or repeatedly connects and disconnects. In addition, a pooled connection can be used repeatedly by multiple applications.
OLE DB has a pooling feature, called session pooling, optimized for improving connectivity performance in large Web database applications. Session pooling preserves connection security and other properties.
A pooled connection is only reused if matching requests are made from both sides of the connection. This means that you do not have to configure your application, server, or database to use session pooling. However, if your provider does not support session pooling by default, you need to create a registry setting to enable session pooling. If you want your ODBC driver to participate in connection pooling you must configure your specific database driver and then set the driver's CPTimeout property in the Windows registry.
The CPTimeout property determines the length of time that a connection remains in the connection pool. If the connection remains in the pool longer than the duration set by CPTimeout , the connection is closed and removed from the pool. The default value for CPTimeout is 60 seconds. You can selectively set the CPTimeout property to enable connection pooling for a specific ODBC database driver by creating a registry key with the following settings:. For example, the following key sets the connection pool timeout to seconds 3 minutes for the SQL Server driver.
Although you can reuse a connection across multiple pages by storing the connection in ASP's Application object, doing so may unnecessarily keep open a connection open, defeating the advantages of using connection pooling.
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