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"feature.callList.enabled" set to No (0).
Minimizing phone logging can also improve performance by reducing the size and frequency of the log files being sent:
"log log.render.level" set to 6 (this logs critical errors only)
"log.render.file.upload.append.sizeLimit" set to 128
If you are looking for other options that may be of interest Greig Sheridan has an interesting blog post on some useful settings especially if you have offices outside of the USA. The settings are updated from time to time so worth checking back at https://greiginsydney.com/optimising-the-polycom-vvx-for-lync/
NOTE: If you are using Skype for Business Online or have enabled in-band phone settings for your Skype for Business server you will get the provisioning server options set back to FTP continually. This stops the phone from getting its configuration from UDM Pro. If this is the case we recommend creating a Device Profile with the following three parameters, then apply this to the All Devices and Approved Devices Tag in the Tags screen.
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