Registry settings
Applies to: 
SQL Server
Azure SQL Database
Azure SQL Managed Instance
Azure Synapse Analytics
Analytics Platform System (PDW)
Each major version of the OLE DB Driver for SQL Server uses its own set of registry settings. The following are the version specific base registry keys (referred to as {base_registry_key} later on):
- HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\MSSQLServer\Client\SNI
{major_version}.0 - HKEY_LOCAL_MACHINE\SOFTWARE\WOW6432Node\Microsoft\MSSQLServer\Client\SNI
{major_version}.0
Replace the {major_version} placeholder in the above keys depending on the major version of the driver, for example: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\MSSQLServer\Client\SNI19.0 is the base key for versions 19.x.x.
Encryption and certificate validation
Force protocol encryption
Encryption can be controlled through the Value field of the {base_registry_key}\GeneralFlags\Flag1 registry entry.
Valid values are 0, 1, or 2 (which maps to Optional, Mandatory, and Strict connection property/keyword values respectively). The OLE DB driver chooses the most secure option between the registry and the connection property/keyword settings.
Trust server certificate
Certificate validation can be controlled through the Value field of the {base_registry_key}\GeneralFlags\Flag2 registry entry.
Valid values are 0 or 1. The OLE DB driver chooses the most secure option between the registry and the connection property/keyword settings. That is, the driver will validate the server certificate as long as at least one of the registry/connection settings enables server certificate validation.
TCP Keep-Alive and Protocol Order registry properties
For MSOLEDBSQL driver versions 19.1 and above, Protocol Order, TCP Keep-Alive, and Keep-Alive Interval can be adjusted in the following registry entries:
- Protocol Order:
{base_registry_key}\ProtocolOrder - TCP Keep-Alive:
{base_registry_key}\tcp\Property2\Value - TCP Keep-Alive Interval:
{base_registry_key}\tcp\Property3\Value
The Protocol Order property is an ordered sequence of null-terminated strings that represent supported protocols. The default Protocol Order value is sm tcp np.
The TCP Keep-Alive parameter (in milliseconds) controls how often TCP attempts to verify that an idle connection is still intact by sending a KEEPALIVE packet. The default is 30,000 milliseconds.
The Keep-Alive Interval parameter (in milliseconds) determines the interval separating KEEPALIVE retransmissions until a response is received. The default is 1000 milliseconds.
See also
Encryption and certificate validation
MSOLEDBSQL major version differences