关于Oracle Clusterware 进程

The Oracle Clusterware Stack

Oracle Clusterware consists of two separate stacks: an upper stack anchored by the Cluster Ready Services (CRS) daemon (crsd) and a lower stack anchored by the Oracle High Availability Services daemon (ohasd). These two stacks have several processes that facilitate cluster operations. The following sections describe these stacks in more detail:

• The Cluster Ready Services Stack

• The Oracle High Availability Services Stack

The Cluster Ready Services Stack

The list in this section describes the processes that comprise CRS. The list includes components that are processes on Linux and UNIX operating systems, or services on Windows.

• Cluster Ready Services (CRS): The primary program for managing high availability operations in a cluster.

  The CRS daemon (crsd) manages cluster resources based on the configuration information that is stored in OCR for each resource. This includes start, stop, monitor, and failover operations. The crsd process generates events when the status of a resource changes. When you have Oracle RAC installed, the crsd process monitors the Oracle database instance, listener, and so on, and automatically restarts these components when a failure occurs.

• Cluster Synchronization Services (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 interface with your clusterware to manage node membership information.

  The cssdagent process monitors the cluster and provides I/O fencing. This service formerly was provided by Oracle Process Monitor Daemon (oprocd), also known as OraFenceService on Windows. A cssdagent failure may result in Oracle Clusterware restarting the node.

• Oracle ASM: Provides disk management for Oracle Clusterware and Oracle Database.

• Cluster Time Synchronization Service (CTSS): Provides time management in a cluster for Oracle Clusterware.

• Event Management (EVM): A background process that publishes events that Oracle Clusterware creates.

• Oracle Notification Service (ONS): A publish and subscribe service for communicating Fast Application Notification (FAN) events.

• Oracle Agent (oraagent): Extends clusterware to support Oracle-specific requirements and complex resources. This process runs server callout scripts when FAN events occur. This process was known as RACG in Oracle Clusterware 11g release 1 (11.1).

• Oracle Root Agent (orarootagent): A specialized oraagent process that helps crsd manage resources owned by root, such as the network, and the Grid virtual IP address.

The Cluster Synchronization Service (CSS), Event Management (EVM), and Oracle Notification Services (ONS) components communicate with other cluster component layers on other nodes in the same cluster database environment. These components are also the main communication links between Oracle Database, applications, and the Oracle Clusterware high availability components. In addition, these background processes monitor and manage database operations.

The Oracle High Availability Services Stack

This section describes the processes that comprise the Oracle High Availability Services stack. The list includes components that are processes on Linux and UNIX operating systems, or services on Windows.

• Cluster Logger Service (ologgerd): Receives information from all the nodes in the cluster and persists in a CHM repository-based database. This service runs on only two nodes in a cluster.

• System Monitor Service (osysmond): The monitoring and operating system metric collection service that sends the data to the cluster logger service. This service runs on every node in a cluster.

• Grid Plug and Play (GPNPD): Provides access to the Grid Plug and Play profile, and coordinates updates to the profile among the nodes of the cluster to ensure that all of the nodes have the most recent profile.

• Grid Interprocess Communication (GIPC): A support daemon that enables Redundant Interconnect Usage.

• Multicast Domain Name Service (mDNS): Used by Grid Plug and Play to locate profiles in the cluster, as well as by GNS to perform name resolution. The mDNS process is a background process on Linux and UNIX and on Windows.

• Oracle Grid Naming Service (GNS): Handles requests sent by external DNS servers, performing name resolution for names defined by the cluster.

Table 1-1 lists the processes and services associated with Oracle Clusterware components. In Table 1-1, if a UNIX or a Linux system process has an (r) beside it, then the process runs as the root user.

Table 1-1 List of Processes and Services Associated with Oracle Clusterware Components

Oracle Clusterware Component	Linux/UNIX Process	Windows Services	Windows Processes
CRS	crsd.bin (r)	OracleOHService	crsd.exe
CSS	ocssd.bin, cssdmonitor,cssdagent	OracleOHService	cssdagent.exe, cssdmonitor.exeocssd.exe
CTSS	octssd.bin (r)		octssd.exe
EVM	evmd.bin, evmlogger.bin	OracleOHService	evmd.exe
GIPC	gipcd.bin
GNS	gnsd (r)		gnsd.exe
Grid Plug and Play	gpnpd.bin	OracleOHService	gpnpd.exe
LOGGER	ologgerd.bin (r)		ologgerd.exe
Master Diskmon	diskmon.bin
mDNS	mdnsd.bin		mDNSResponder.exe
Oracle agent	oraagent.bin (11.2), or racgmainand racgimon (11.1)		oraagent.exe
Oracle High Availability Services	ohasd.bin (r)	OracleOHService	ohasd.exe
ONS	ons		ons.exe
Oracle root agent	orarootagent (r)		orarootagent.exe
SYSMON	osysmond.bin (r)		osysmond.exe

Note:

Oracle Clusterware on Linux platforms can have multiple threads that appear as separate processes with unique process identifiers.

Figure 1-2 illustrates cluster startup.