What’s New in R139 ? OS updates and VCD-support for HCX-OSAM.
Critical HCX Manager Web-Engine OOM condition resolved.
This is not a new feature – but the use of the broadcast system to notify of a required upgrade is new. The OOM condition can affect in-support releases R136-R138. The following banner was broadcasted to subscribed systems:

Enhancement to OS-Assisted Migrations
Update to Certified Operating Systems
OS-Assisted Migrations enable the conversion and migration of KVM/Hyper-V virtual machines into a vSphere environment using the HCX-style workflows. HCX R139 certifies support for migrating CentOS 7.X virtual machines in Hyper-V environments.
Read the OSAM launch blog.
Read Understanding OS Assisted Migration in VMware docs.
Support added for vCloud Director-based Clouds
OS-Assisted Migrations enable the conversion and migration of KVM/Hyper-V virtual machines into a vSphere environment using the HCX-style workflows. HCX R139 adds support for HCX Cloud installations integrated with vCloud Director.
Quick Note: HCX for vCloud Director is currently available to limited to dedicated design partners.
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Bug Fixes
PR/2201967 – Resolved an issue where vMotion migrations fail in vSphere environments where the migrated virtual machines exist on ESXi 5.5 hosts and are managed by a 6.5 Virtual Center server.
PR/2538477 – Resolved an issue causing slow responsiveness in the HCX Migration user interface in environments with vSphere inventories that have a large number of networks.
PR/2540972 – Resolved an issue that prevented the Network Extension configuration page from rendering correctly.
PR/2540975 – Resolved an issue preventing the proper execution of configuration and migration workflows on HCX Connector or HCX Cloud Manager after seven days uptime with service update R138.
PR/2544433 – Resolved an issue with the HCX Connector or Cloud Manager web-engine service becoming unresponsive due to memory exhaustion.