With parallel concurrent processing, each node with concurrent managers may or may not be running an ORACLE instance. On a node that is not running ORACLE, the concurrent manager(s) connect via SQL*Net to a node that is running ORACLE.
Concurrent program executable files, along with log and report output files, can be stored on a node's local disk. Alternatively, these files can be stored in one central location, and read remotely from other nodes.
Database Instances, Manager Location, and File Distribution
Examples of Parallel Concurrent Processing
Installing Parallel Concurrent Processing
Nodes field help