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About Oracle RAC Background Processes

The GCS and GES processes, and the GRD collaborate to enable Cache Fusion. The

Oracle RAC processes and their identifiers are as follows:

• ACMS: Atomic Controlfile to Memory Service (ACMS)

In an Oracle RAC environment, the ACMS per-instance process is an agent that

contributes to ensuring a distributed SGA memory update is either globally

committed on success or globally aborted if a failure occurs.

• GTX0-j: Global Transaction Process

The GTX0-j process provides transparent support for XA global transactions in an

Oracle RAC environment. The database autotunes the number of these processes

based on the workload of XA global transactions.

•  LMON: Global Enqueue Service Monitor

The LMON process monitors global enqueues and resources across the cluster and

performs global enqueue recovery operations.

• LMD: Global Enqueue Service Daemon

The LMD process manages incoming remote resource requests within each

instance.

•  LMS: Global Cache Service Process

The LMS process maintains records of the data file statuses and each cached block

by recording information in a Global Resource Directory (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
.

• LCK0: Instance Enqueue Process

The LCK0 process manages non-Cache Fusion resource requests such as library

and row cache requests.

•  RMSn: Oracle RAC Management Processes (RMSn)

The RMSn processes perform manageability tasks for Oracle RAC. Tasks

accomplished by an RMSn process include creation of resources related to Oracle

RAC when new instances are added to the clusters.

•  RSMN: Remote Slave Monitor manages background slave process creation and

communication on remote instances. These background slave processes perform

tasks on behalf of a coordinating process running in another instance.


Important Note: Many of the Oracle Database components that this section
describes are in addition to the components that are described for
noncluster Oracle databases in Oracle Database Concepts.