Explanation/Reference:
Note:
* A Node Manager process is not associated with a specific WebLogic domain but with a machine. You can use the same Node Manager process to control server instances in any WebLogic Server domain, as long as the server instances reside on the same machine as the Node Manager process. Node Manager must run on each computer that hosts WebLogic Server instances-whether Administration Server or Managed Server-that you want to control with Node Manager.
* In managing multiple servers, Node Manager uses multiple configuration files and outputs log files to multiple directories.
* nodemanager.domains
This file contains mappings between the names of domains managed by Node Manager and their corresponding directories.
* Node Manager in the WebLogic Server Environment

Reference; Node Manager Administrator's Guide for Oracle WebLogic Server 12c