2.3.3. Reading and Writing Configuration Parameter Values

Functions such as NCM_GetValue( ) and NCM_SetValue( ) that enable you to read or write a configuration parameter value in the system configuration require that you specify the parameter's scope. Such functions accept the NCMFamily and NCMDevice structures as input, and it is through these structures that you specify the parameter's scope. Set these structures as follows depending on the type of parameter you wish to modify:

• device-specific configuration parameters: NCMDevice should be set to a valid address.
• family level configuration parameters: NCMFamily should be set to a valid address.
• global configuration parameters: NCMFamily and NCMDevice should be set to NULL.

  The NCM_GetVariables( ) function can be used to retrieve a list of all global configuration parameters from the DCM Catalog by setting both the NCMFamily and NCMDevice structures to NULL.

• overridable configuration parameters: to treat the parameter globally, set the value of the NCMFamily and NCMDevice structures as you would a global parameter, both to NULL; to treat the parameter at the device level, set the value of the NCMFamily and NCMDevice structures as you would a device-level parameter, both set to a valid address.

  Note: The DCM Catalog maintains two copies of overridable configuration parameters, one at the global level, and another for each device. By default, the device-level copy is updated whenever the global-level copy is modified. But once the device-level copy is modified, its value is de-linked from the global-level copy. Changes to the global-level no longer affect that device.

This method for accessing different levels of data is summarized in Table 1, Configuration Parameter Level Control.

Table 1. Configuration Parameter Level Control

Parameter Scope	Value of NCMFamily	Value of NCMDevice
Device	Pointer to family	Pointer to device
Family	Pointer to a family	NULL
Global	NULL	NULL
Global overridable, treated as global	NULL	NULL
Global overridable, treated as device-specific	Pointer to family	Pointer to device

Note: There are several parameters for Antares products that are global in scope and are retrieved through the Antares Global Settings family. The parameters are: Bulk_Data_Buffer, DspAskToken, DspWaitCall, Max_Bulk_Data_Buffer, Max_Bulk_Data, Max_Dpi, Max_Opened_Rcus, Max_Rcus, Message_Length.

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