Creating a Driver Application - Multithreaded Applications
Applies to: 
SQL Server
Azure SQL Database
Azure SQL Managed Instance
Azure Synapse Analytics
Analytics Platform System (PDW)
Important
SQL Server Native Client (SNAC) isn't shipped with:
- SQL Server 2022 (16.x) and later versions
- SQL Server Management Studio 19 and later versions
The SQL Server Native Client (SQLNCLI or SQLNCLI11) and the legacy Microsoft OLE DB Provider for SQL Server (SQLOLEDB) aren't recommended for new application development.
For new projects, use one of the following drivers:
For SQLNCLI that ships as a component of SQL Server Database Engine (versions 2012 through 2019), see this Support Lifecycle exception.
The SQL Server Native Client ODBC driver is a multithreaded driver. Writing a multithreaded application is an alternative to using asynchronous calls to process multiple ODBC calls. A thread can make a synchronous ODBC call, and other threads can process while the first thread is blocked waiting for the response to its call. This model is more efficient than making asynchronous calls because it eliminates overhead such as network traffic and making repeated ODBC function calls testing for SQL_STILL_EXECUTING.
Asynchronous mode is still an effective method of processing. The performance improvements of a multithreaded model are not enough to justify rewriting asynchronous applications. If users are converting DB-Library applications that use the DB-Library asynchronous model, it is easier to convert them to the ODBC asynchronous model.