Oracle Cluster Specific Daemons:
Crsd :
The CRS daemon (crsd) manages cluster resources based
on configuration information that is stored in Oracle Cluster Registry (OCR)
for each resource. This includes start, stop, monitor, and failover operations.
The crsd process generates events when the status of a resource changes.
Cssd :
Cluster Synchronization Service (CSS): Manages
the cluster configuration by controlling which nodes are members of the cluster
and by notifying members when a node joins or leaves the cluster. If you are
using certified third-party clusterware, then CSS processes interfaces with
your clusterware to manage node membership information. CSS has three separate
processes: the CSS daemon (ocssd), the CSS Agent (cssdagent), and the CSS
Monitor (cssdmonitor). The cssdagent process monitors the cluster and provides
input/output fencing. This service formerly was provided by Oracle Process
Monitor daemon (oprocd), also known as OraFenceService on Windows. A cssdagent
failure results in Oracle Clusterware restarting the node.
Diskmon :
Disk Monitor daemon (diskmon): Monitors and performs
input/output fencing for Oracle Exadata Storage Server. As Exadata storage can
be added to any Oracle RAC node at any point in time, the diskmon daemon is
always started when ocssd is started.
Evmd :
Event Manager (EVM): Is a background process that
publishes Oracle Clusterware events
Mdnsd :
Multicast domain name service (mDNS): Allows DNS
requests. The mDNS process is a background process on Linux and UNIX, and a
service on Windows.
Gnsd :
Oracle Grid Naming Service (GNS): Is a gateway between
the cluster mDNS and external DNS servers. The GNS process performs name
resolution within the cluster.
Ons :
Oracle Notification Service (ONS): Is a
publish-and-subscribe service for communicating Fast Application Notification
(FAN) events
Oraagent :
oraagent: Extends clusterware to support Oracle-specific
requirements and complex resources. It runs server callout scripts when FAN
events occur. This process was known as RACG in Oracle Clusterware 11g Release
1 (11.1).
Orarootagent :
Oracle root agent (orarootagent): Is a specialized
oraagent process that helps CRSD manage resources owned by root, such as the
network, and the Grid virtual IP address
Oclskd :
Cluster kill daemon (oclskd): Handles instance/node
evictions requests that have been escalated to CSS .
Gipcd :
Grid IPC daemon (gipcd): Is a helper daemon for the
communications infrastructure
Ctssd :
Cluster time synchronisation daemon(ctssd) to manage
the time syncrhonization between nodes, rather depending on NTP.
LMSn — Global Cache
Service Process: It can mainly handle the cache fusion part. It
handles the consistent copies of blocks that are transferred between instances.
It receives the request from the LMD to perform lock requests. It rolls back
any uncommitted transactions. There can be up to 10 LMS process running and can
be started dynamically if demand requires. It also handles the global deadlock
detections and monitors for the lock conversion timeouts.
LMON —
Global Enqueue Service Monitor: This process manages the GES, it maintains
the consistency of GCSmemory in case of process death. It also responsible for
cluster reconfiguration and locks reconfiguration.
LMD — Global Enqueue Service Daemon: This manages eneque manager service request for the GCS. It also handles the deadlock detections and remote resource requests the other instances.
LCK0 — Instance Enqueue Process: Manages the instance resource requests and cross instance call operations for shared resources. It builds a list of invalid lock elements and validates the lock elements during recovery.
DIAG — Diagnosability Daemon
GES maintains or handles the synchronization of the dictionary cache,
library cache, transaction locks, and DDL locks. In other words, GES manages
enqueues other than data blocks. To synchronize access to the data dictionary
cache, latches are used in exclusive (X) mode and in single-node cluster
databases. Global enqueues are used in cluster database mode
GCS ensures a single system
image of the data even though the data is accessed by multiple instances.