You can read and modify parameters in online and offline devices.
Online Devices
You can read and modify parameter values in an online device. When you modify parameter values for an online device, the value is stored in both the device and in the configuration database. (The value is written to the device and read back from the device. If the write and read are successful, the value is stored in the database.) Remember that any parameter modifications made at the device level affect only that device. Any new devices of the same type inherit the parameter values specified in the device revision. To modify parameters, right-click the device, and select Modify Parameters.
Offline Devices
If you attempt to modify parameters in an offline device, you will receive a message that the DeltaV system cannot communicate with the device and you are given the option of modifying parameters offline. When you modify parameter values in an offline device, the values are stored in the database only. Later, you can download the device to synchronize the values in the database with the values in the device.
NVRAM Button
Some devices require an explicit command to save parameter values in non-volatile memory. If you are modifying parameter values for a device with this requirement, the NVRAM button is enabled on the Modify Parameters dialog. Click this button to save the parameter values to non-volatile memory. If you download the parameters to a device with this requirement, the save command is sent automatically if the parameter download is successful.