1 Introduction to Oracle Clusterware

What is Oracle Clusterware?

Oracle Clusterware enables servers to communicate with each other, so that they appear to function as a collective unit. This combination of servers is commonly known as a cluster. Although the servers are standalone servers, each server has additional processes that communicate with other servers. In this way the separate servers appear as if they are one system to applications and end users.

Oracle Clusterware provides the infrastructure necessary to run Oracle Real Application Clusters (Oracle RAC). Oracle Clusterware also manages resources, such as virtual IP (VIP) addresses, databases, listeners, services, and so on. These resources are generally named ora.host_name.resource_name. Oracle does not support editing these resources except under the explicit direction of My Oracle Support.

Figure 1-1 shows a configuration that uses Oracle Clusterware to extend the basic single-instance Oracle Database architecture. In Figure 1-1, the cluster is running Oracle Database and is actively servicing applications and users. Using Oracle Clusterware, you can use the same high availability mechanisms to make your Oracle database and your custom applications highly available.

Figure 1-1 Oracle Clusterware Configuration

Description of "Figure 1-1 Oracle Clusterware Configuration"

The benefits of using a cluster include:

• Scalability of applications

• Reduce total cost of ownership for the infrastructure by providing a scalable system with low-cost commodity hardware

• Ability to fail over

• Increase throughput on demand for cluster-aware applications, by adding servers to a cluster to increase cluster resources

• Increase throughput for cluster-aware applications by enabling the applications to run on all of the nodes in a cluster

• Ability to program the startup of applications in a planned order that ensures dependent processes are started

• Ability to monitor processes and restart them if they stop

• Eliminate unplanned downtime due to hardware or software malfunctions

• Reduce or eliminate planned downtime for software maintenance

You can program Oracle Clusterware to manage the availability of user applications and Oracle databases. In an Oracle RAC environment, Oracle Clusterware manages all of the resources automatically. All of the applications and processes that Oracle Clusterware manages are either cluster resources or local resources.

Oracle Clusterware is required for using Oracle RAC; it is the only clusterware that you need for platforms on which Oracle RAC operates. Although Oracle RAC continues to support many third-party clusterware products on specific platforms, you must also install and use Oracle Clusterware. Note that the servers on which you want to install and run Oracle Clusterware must use the same operating system.

Using Oracle Clusterware eliminates the need for proprietary vendor clusterware and provides the benefit of using only Oracle software. Oracle provides an entire software solution, including everything from disk management with Oracle Automatic Storage Management (Oracle ASM) to data management with Oracle Database and Oracle RAC. In addition, Oracle Database features, such as Oracle Services, provide advanced functionality when used with the underlying Oracle Clusterware high availability framework.

Oracle Clusterware has two stored components, besides the binaries: The voting disk files, which record node membership information, and the Oracle Cluster Registry (OCR), which records cluster configuration information. Voting disks and OCRs must reside on shared storage available to all cluster member nodes.

Understanding System Requirements for Oracle Clusterware

To use Oracle Clusterware, you must understand the hardware and software concepts and requirements as described in the following sections:

• Oracle Clusterware Hardware Concepts and Requirements

• Oracle Clusterware Operating System Concepts and Requirements

• Oracle Clusterware Software Concepts and Requirements

• Oracle Clusterware Network Configuration Concepts

• Overview of Upgrading Oracle Clusterware

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mycluster.example.com NS myclustergns.example.com
#Let the world know to go to the GNS vip
myclustergns.example.com. 10.9.8.7

Overview of Oracle Clusterware Platform-Specific Software Components

When Oracle Clusterware is operational, several platform-specific processes or services run on each node in the cluster. This section describes these various processes and services.

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.exe ocssd.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 racgmain and 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

See Also:

"Clusterware Log Files and the Unified Log Directory Structure" for information about the location of log files created for processes

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.

Figure 1-2 Cluster Startup

Description of "Figure 1-2 Cluster Startup"

Overview of Installing Oracle Clusterware

The following section introduces the installation processes for Oracle Clusterware.

Overview of Upgrading Oracle Clusterware

Oracle supports in-place and out-of-place upgrades. Both strategies facilitate rolling upgrades. For Oracle Clusterware 11g release 2 (11.2), in-place upgrades are supported for patches only. Patch bundles and one-off patches are supported for in-place upgrades but patch sets and major point releases are supported for out-of-place upgrades only.

An in-place upgrade replaces the Oracle Clusterware software with the newer version in the same Grid home. Out-of-place upgrade has both versions of the same software present on the nodes at the same time, in different Grid homes, but only one version is active.

Rolling upgrades avoid downtime and ensure continuous availability of Oracle Clusterware while the software is upgraded to the new version. When you upgrade to 11g release 2 (11.2), Oracle Clusterware and Oracle ASM binaries are installed as a single binary called the Grid Infrastructure. You can upgrade Oracle Clusterware in a rolling manner from Oracle Clusterware 10g and Oracle Clusterware 11g, however you can only upgrade Oracle ASM in a rolling manner from Oracle Database 11g release 1 (11.1).

Overview of Managing Oracle Clusterware Environments

The following list describes the tools and utilities for managing your Oracle Clusterware environment:

• Oracle Enterprise Manager: Oracle Enterprise Manager has both the Database Control and Grid Control GUI interfaces for managing both single instance and Oracle RAC database environments. It also has GUI interfaces to manage Oracle Clusterware and all components configured in the Oracle Grid Infrastructure installation. Oracle recommends that you use Oracle Enterprise Manager to perform administrative tasks.

  See Also:

  Oracle Database 2 Day + Real Application Clusters Guide, Oracle Real Application Clusters Administration and Deployment Guide, and Oracle Enterprise Manager online documentation for more information about administering Oracle Clusterware with Oracle Enterprise Manager

• Cluster Verification Utility (CVU): CVU is a command-line utility that you use to verify a range of cluster and Oracle RAC specific components. Use CVU to verify shared storage devices, networking configurations, system requirements, and Oracle Clusterware, and operating system groups and users.

  Install and use CVU for both preinstallation and postinstallation checks of your cluster environment. CVU is especially useful during preinstallation and during installation of Oracle Clusterware and Oracle RAC components to ensure that your configuration meets the minimum installation requirements. Also use CVU to verify your configuration after completing administrative tasks, such as node additions and node deletions.

  See Also:

  Your platform-specific Oracle Clusterware and Oracle RAC installation guide for information about how to manually install CVU, and Appendix A, "Cluster Verification Utility Reference" for more information about using CVU

• Server Control (SRVCTL): SRVCTL is a command-line interface that you can use to manage Oracle resources, such as databases, services, or listeners in the cluster.

  Note:

  You can only manage server pools that have names prefixed with ora.* by using SRVCTL.

  See Also:

  Server Control Utility reference appendix in the Oracle Real Application Clusters Administration and Deployment Guide

• Oracle Clusterware Control (CRSCTL): CRSCTL is a command-line tool that you can use to manage Oracle Clusterware. CRSCTL should be used for general clusterware management and management of individual resources.

  Oracle Clusterware 11g release 2 (11.2) introduces cluster-aware commands with which you can perform operations from any node in the cluster on another node in the cluster, or on all nodes in the cluster, depending on the operation.

  You can use crsctl commands to monitor cluster resources (crsctl status resource) and to monitor and manage servers and server pools other than server pools that have names prefixed with ora.*, such as crsctl status server, crsctl status serverpool, crsctl modify serverpool, and crsctl relocate server. You can also manage Oracle High Availability Services on the entire cluster (crsctl start | stop | enable | disable | config crs), using the optional node-specific arguments -n or -all. You also can use CRSCTL to manage Oracle Clusterware on individual nodes (crsctl start | stop | enable | disable | config crs).

  See Also:

  • Chapter 2, "Administering Oracle Clusterware" for more information about using crsctl commands to manage Oracle Clusterware

  • Appendix E, "CRSCTL Utility Reference" for a complete list of CRSCTL commands

• Oracle Interface Configuration Tool (OIFCFG): OIFCFG is a command-line tool for both single-instance Oracle databases and Oracle RAC environments. Use OIFCFG to allocate and deallocate network interfaces to components. You can also use OIFCFG to direct components to use specific network interfaces and to retrieve component configuration information.

  See Also:

  Appendix D, "Oracle Interface Configuration Tool (OIFCFG) Command Reference"

• Oracle Cluster Registry Configuration Tool (OCRCONFIG): OCRCONFIG is a command-line tool for OCR administration. You can also use the OCRCHECK and OCRDUMP utilities to troubleshoot configuration problems that affect OCR.

  See Also:

  Chapter 2, "Administering Oracle Clusterware" for more information about managing OCR

• Cluster Health Monitor (CHM): CHM detects and analyzes operating system and cluster resource-related degradation and failures to provide more details to users for many Oracle Clusterware and Oracle RAC issues, such as node eviction. The tool continuously tracks the operating system resource consumption at the node, process, and device levels. It collects and analyzes the clusterwide data. In real-time mode, when thresholds are met, the tool shows an alert to the user. For root-cause analysis, historical data can be replayed to understand what was happening at the time of failure.

  See Also:

  "Cluster Health Monitor" for more information about CHM

Overview of Cloning and Extending Oracle Clusterware in Grid Environments

Cloning nodes is the preferred method of creating new clusters. The cloning process copies Oracle Clusterware software images to other nodes that have similar hardware and software. Use cloning to quickly create several clusters of the same configuration. Before using cloning, you must install an Oracle Clusterware home successfully on at least one node using the instructions in your platform-specific Oracle Clusterware installation guide.

For new installations, or if you must install on only one cluster, Oracle recommends that you use the automated and interactive installation methods, such as Oracle Universal Installer or the Provisioning Pack feature of Oracle Enterprise Manager. These methods perform installation checks to ensure a successful installation. To add or delete Oracle Clusterware from nodes in the cluster, use the addNode.sh and rootcrs.pl scripts.

Overview of the Oracle Clusterware High Availability Framework and APIs

Oracle Clusterware provides many high availability application programming interfaces called CLSCRS APIs that you use to enable Oracle Clusterware to manage applications or processes that run in a cluster. The CLSCRS APIs enable you to provide high availability for all of your applications.

You can define a VIP address for an application to enable users to access the application independently of the node in the cluster on which the application is running. This is referred to as the application VIP. You can define multiple application VIPs, with generally one application VIP defined for each application running. The application VIP is related to the application by making it dependent on the application resource defined by Oracle Clusterware.

To maintain high availability, Oracle Clusterware components can respond to status changes to restart applications and processes according to defined high availability rules. You can use the Oracle Clusterware high availability framework by registering your applications with Oracle Clusterware and configuring the clusterware to start, stop, or relocate your application processes. That is, you can make custom applications highly available by using Oracle Clusterware to create profiles that monitor, relocate, and restart your applications.