Performance Considerations

Application Using Threads (ApplicationUsingThreads): The driver coordinates concurrent database operations (operations from different threads) by acquiring locks. Although locking prevents errors in the driver, it also decreases performance. If your application does not make ODBC calls from different threads, the driver has no reason to coordinate operations. In this case, the ApplicationUsingThreads attribute should be disabled (set to 0).

NOTE: If you are using a multi-threaded application, you must enable the Application Using Threads option.

Connection Pooling (ConnectionPooling): If you enable the driver to use connection pooling, you can set additional options that affect performance:

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Load Balance Timeout: You can define how long to keep connections in the pool. The time that a connection was last used is compared to the current time and, if the timespan exceeds the value of the Load Balance Timeout option, the connection is destroyed. The Min Pool Size option can cause some connections to ignore this value.

■	Connection Reset: Resetting a re-used connection to the initial configuration settings impacts performance negatively because the connection must issue additional commands to the server.

■	Max Pool Size: Setting the maximum number of connections that the pool can contain too low might cause delays while waiting for a connection to become available. Setting the number too high wastes resources.

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Min Pool Size: A connection pool is created when the first connection with a unique connection string connects to the database. The pool is populated with connections up to the minimum pool size, if one has been specified. The connection pool retains this number of connections, even when some connections exceed their Load Balance Timeout value.

Enable Bulk Load: For batch inserts and individual inserts, updates, and deletes, the driver can use the Salesforce Bulk API instead of the Web service API. Using the Bulk API significantly reduces the number of Web service calls the driver uses to transfer data to Salesforce and may improve performance.

Fetch Size/WS Fetch Size: The connection options Fetch Size and WSFetch Size can be used to adjust the trade-off between throughput and response time. In general, setting larger values for WSFetch Size and Fetch Size will improve throughput, but can reduce response time.

For example, if an application attempts to fetch 100,000 rows from the remote data source and WSFetch Size is set to 500, the driver must make 200 Web service calls to get the 100,000 rows. If, however, WSFetch Size is set to 2000 (the maximum), the driver only needs to make 50 Web service calls to retrieve 100,000 rows. Web service calls are expensive, so generally, minimizing Web service calls increases throughput. In addition, many Cloud data sources impose limits on the number of Web service calls that can be made in a given period of time. Minimizing the number of Web service calls used to fetch data also can help prevent exceeding the data source call limits.

For many applications, throughput is the primary performance measure, but for interactive applications, such as Web applications, response time (how fast the first set of data is returned) is more important than throughput. For example, suppose that you have a Web application that displays data 50 rows to a page and that, on average, you view three or four pages. Response time can be improved by setting Fetch Size to 50 (the number of rows displayed on a page) and WSFetch Size to 200. With these settings, the driver fetches all of the rows from the remote data source that you would typically view in a single Web service call and only processes the rows needed to display the first page.