Oracle RAC Components and Background Process

Oracle RAC is composed of two or more database instances.
They are composed of Memory structures and background processes same as the single instance database.

Oracle RAC instances use two processes:
1- GES(Global Enqueue Service)
2- GCS(Global Cache Service) that enable cache fusion.

Oracle RAC instances are composed of following background processes:
ACMS—Atomic Controlfile to Memory Service (ACMS)
GTX0-j—Global Transaction Process
LMON—Global Enqueue Service Monitor
LMD—Global Enqueue Service Daemon
LMS—Global Cache Service Process
LCK0—Instance Enqueue Process
RMSn—Oracle RAC Management Processes (RMSn)
RSMN—Remote Slave Monitor