Configuration items in the Phone/Device Specific Config area (sometimes referred to as the 'vendor config' data) are stored as a block of XML in the CUCM database. Depending on the device (and the possible size of this chunk of XML), the data may be stored in the devicexml4k/devicexml8k/devicexml16k tables. See this FAQ for info on some stored procedures that make this a bit easier to deal with:
https://developer.cisco.com/site/axl/help/faqs/index.gsp#section-1
The actual content of the XML consists of elements which describe the device specific config settings. Unfortunately there is no available schema describing the XML for this content, though the fields are generally pretty self explanatory. Also, note that generally the XML for any given device will be empty until a specific config is changed, in which case generally only the changed XML config element will be present.
In order to perform the operation you describe, you will need to do something like:
- Know the XML element and values needed to enable/disable the setting (typically by changing the setting in CUCM, then reading the XML to see what values are present)
- For each device, read the existing vendor config XML data for the device,
- Iterate through the XML elements to see if the particular config element you are interested in is present - if not, add it
- Set the desired value
- Write the XML chunk back to CUCM
