Global Resource Background Processes

• Atomic Control File to Memory Service (ACMS): In a RAC environment, the ACMS per-instance process is an agent that contributes to ensuring that a distributed SGA memory update is either globally committed on success or globally aborted if a failure occurs.
• Global Enqueue Service Monitor (LMON): The LMON process monitors global enqueues and resources across the cluster and performs global enqueue recovery operations.
• Global Enqueue Service Daemon (LMD): The LMD process manages incoming remote resource requests within each instance.
• Global Cache Service Process (LMS): The LMS process maintains records of the data file statuses and each cached block by recording information in the GRD. The LMS process also controls the flow of messages to remote instances and manages global data block access and transmits block images between the buffer caches of different instances. This processing is part of the cache fusion feature.
• Instance Enqueue Process (LCK0): The LCK0 process manages noncache fusion resource requests such as library and row cache requests.
• Global Cache/Enqueue Service Heartbeat Monitor (LMHB): LMHB monitors LMON, LMD, and LMSn processes to ensure that they are running normally without blocking or spinning.
• Result Cache Background Process (RCBG): This process is used for handling invalidation and other messages generated by server processes attached to other instances in Oracle RAC.