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Introduction

Oracle Real Application Clusters Guard provides an enhanced configuration of Oracle Real Application Clusters on Microsoft Windows. It tightly integrates Oracle Real Application Clusters with the Microsoft Cluster Server software to provide a configuration that leverages the high-availability technologies of all.

This chapter discusses the following topics:

Topic	Reference
Benefits of Oracle Real Application Clusters Guard	Section 1.1
Components for Running Oracle Real Application Clusters Guard	Section 1.2
Oracle Real Application Clusters Guard Ease-of-Use Features	Section 1.3
A Typical Oracle Real Application Clusters Guard Configuration	Section 1.4

1.1 Benefits of Oracle Real Application Clusters Guard

Oracle Real Application Clusters Guard integrates Oracle Real Application Clusters databases with Microsoft Cluster Server software and hardware to make configuration of multi-instance databases into an MSCS cluster easy and to enhance the high-availability features of Oracle Real Application Clusters by offering these additional benefits:

• Optionally restarts failed database instances and listeners in a cluster

• Detects and resolves problems with instance hangs

• Eliminates connect-time failover TCP/IP timeout delays for new connection requests

• Optionally executes a user-written script before or after database instance state (online/offline) changes occur

To understand how Oracle Real Application Clusters Guard works, it is important to understand how each of the required hardware and software components provides high availability. The following sections describe Oracle Real Application Clusters software, MSCS software and Microsoft clusters, and Oracle Real Application Clusters Guard.

1.2 Components for Running Oracle Real Application Clusters Guard

The following components are required for an Oracle Real Application Clusters Guard high-availability solution:

• Oracle Real Application Clusters software

• Microsoft Cluster Server (MSCS) software

• Oracle Real Application Clusters Guard software

• Cluster hardware

The following sections briefly describe how each of these components contributes to the high-availability solution.

1.2.1 Microsoft Cluster Server Software and Microsoft Cluster Hardware

Oracle Real Application Clusters Guard high-availability solutions on Windows use Microsoft cluster hardware and Microsoft Cluster Server (MSCS) software.

• A Microsoft cluster is a configuration of two to four independent computing systems (called cluster nodes) that are connected to the same disk subsystem.

• Microsoft Cluster Server (MSCS) is software that is included with Microsoft Windows NT Enterprise Edition, Microsoft Windows 2000 Advanced Server, and Microsoft Windows 2000 Datacenter Server. It allows you to configure, monitor, and control applications and hardware components (called cluster resources) that are deployed on a Microsoft cluster. Microsoft Windows NT and Microsoft Windows 2000 Advanced Server support up to two nodes in a cluster. Microsoft Windows 2000 Datacenter Server supports up to four nodes in a cluster.

Microsoft Cluster Server software monitors the status of the cluster nodes and the cluster resources and maintains information about the cluster in general (cluster metadata). MSCS detects node failures through an internode network connection and determines resource failures through calls made to the resource. When a node failure occurs, MSCS moves resources from the failed node to a surviving node, through an operation called failover.

MSCS uses a shared-nothing configuration. In a shared-nothing configuration, all nodes are cabled physically to the same NTFS disks, but only one node can access a given disk at a time. Even though all nodes are physically connected to the disks, only the node that owns the disks can access them.

Figure 1-1 shows that if a node in a two-node cluster becomes unavailable, the other cluster node can assume ownership of the shared-nothing disks and application workloads that were owned by the failed node.

When an MSCS cluster is recovering from a failure, a surviving node gains access to the disk data of the failed node through the shared-nothing configuration.

Figure 1-1 Shared-Nothing Configuration

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The quorum resource maintains the configuration data (metadata) necessary for recovery of the cluster in case of a power outage or damage to data in memory. The quorum resource is accessible to other cluster resources so that all cluster nodes have access to the cluster metadata. The quorum resource performs these services:

• Determines which cluster node controls the cluster

• Stores logging information necessary to recover the cluster from a failure

• Maintains access to the most current cluster metadata

Because it is located on an MSCS shared-nothing disk, the quorum resource can be owned by only one cluster node at a time. If a cluster node becomes isolated (cannot communicate with the other cluster nodes because of a network failure, for example), then the node that gains control of the quorum resource takes over the workload of the isolated node.

(To view the location of the quorum resource and the maximum size of the quorum log, select the cluster in the Oracle Real Application Clusters Guard Manager tree view, then click the Quorum tab. To change the location of the quorum resource or the maximum size of the quorum log, open MSCS Cluster Administrator, then in the File menu select Properties, then click the Quorum tab.)

1.2.2 Oracle Real Application Clusters Software

Oracle Real Application Clusters consist of multiple database instances distributed across cluster nodes. Oracle Real Application Clusters software coordinates each node's access to the same database to provide consistency and integrity. In the event of an instance failure, Oracle Real Application Clusters software performs recovery operations for the failed instance so that clients can continue to access the database through a surviving instance on another node.

Unlike resources on MSCS shared-nothing cluster disks, all Oracle Real Application Clusters instances must have concurrent access to raw disks on a shared disk subsystem. The instances write data onto the raw disk partitions to update the data files, control files, and redo log files that all nodes in the cluster share, as shown for a two-node cluster in Figure 1-2. All instances in Oracle Real Application Clusters environments share the same data files and control files. Each instance has its own discrete set of redo log files that also reside on the shared raw disks. During failures, this arrangement of shared access to redo log files allows surviving instances to perform recovery for failed instances. These disks are controlled by the Oracle Real Application Clusters software.

Figure 1-2 Oracle Real Application Clusters Disk Configuration

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1.2.3 Oracle Real Application Clusters Guard Software

Oracle Real Application Clusters Guard software provides wizards and a graphical user interface that simplifies the process of configuring an Oracle Real Application Clusters database into an MSCS cluster. When you configure an Oracle Real Application Clusters database into an MSCS cluster, Oracle Real Application Clusters Guard uses the information it receives about the health of cluster resources from MSCS to determine if and when failed instances and listeners should be restarted, and to detect and resolve problems with instance hangs.

Oracle Real Application Clusters Guard consists of Oracle Services for MSCS and Oracle Real Application Clusters Guard Manager:

• Oracle Services for MSCS works with the MSCS software to monitor Oracle Real Application Clusters database instances for failure (due to hardware or software failures) and for database hangs. When a failed or hung instance is detected, Oracle Real Application Clusters Guard provides the means to return the instance to operational status quickly and automatically.

• Oracle Real Application Clusters Guard Manager provides an easy-to-use interface and wizards that help you to configure and manage Oracle Real Application Clusters database instances in the MSCS cluster, and troubleshooting tools that help you to diagnose problems.

Together, these components enable rapid deployment of Oracle Real Application Clusters databases on an MSCS cluster.

Although the Oracle Real Application Clusters database instances themselves do not use disks configured and managed by MSCS (shared-nothing cluster disks), the quorum disk that maintains configuration data must use shared-nothing cluster disks. Therefore, when you configure an Oracle Real Application Clusters database into a MSCS cluster, both shared-nothing cluster disks and raw disk partitions are required, as shown in Figure 1-3.

Figure 1-3 Disk Configuration for Oracle Real Application Clusters Guard

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Oracle Real Application Clusters Guard supports both the default n-node deployment and primary/secondary instance deployment of Oracle Real Application Clusters.

1.3 Oracle Real Application Clusters Guard Ease-of-Use Features

Considering the numerous hardware and software components involved, configuring databases and their dependent components (IP addresses and network names) to work in an MSCS cluster can be a complex process. Thus, Oracle Real Application Clusters Guard is designed to be easy to install, administer, and use, as described in the following list:

• Installation

  You can install Oracle Real Application Clusters Guard either interactively using the Oracle Universal Installer, or in silent mode. A silent mode installation is an installation method that allows you to install software by supplying input to Oracle Universal Installer with a response file.

• Administration and use

  Oracle Real Application Clusters Guard Manager provides an easy-to-use interface to set up, configure, and manage databases on the cluster. Oracle Real Application Clusters Guard Manager provides wizards that automate the configuration process and that ensure that the configuration is replicated consistently across cluster nodes.

  Oracle Real Application Clusters Guard Manager includes:

  • A tree view of objects that displays multiple views of the same data to help you find information efficiently

  • Wizards that automate and simplify the process of configuring Oracle Real Application Clusters with MSCS

  • An integrated family of verification tools that automatically diagnose and fix common configuration problems both before and after configuration

  • Online documentation, including online help and manuals available in HTML and PDF formats

  • A command-line interface (ORACGCMD) that is useful for managing the cluster through batch programs or scripts

  Figure 1-4 shows an Oracle Real Application Clusters Guard Manager window. The left pane displays a tree view showing multiple views (and the current state) of the cluster nodes and database instances. The right pane displays a property page that lists the nodes and databases configured in the cluster. Depending on the folder you choose from the tree view, the display in the right pane changes. When you select a database, instance, or instance group, the property sheet for that database, instance, or instance group is displayed.

Figure 1-4 Oracle Real Application Clusters Guard Manager Window

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Figure 1-5 shows the Oracle Real Application Clusters Guard Manager menus and the items within each menu.

Figure 1-5 Oracle Real Application Clusters Guard Manager Menus and Contents

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1.4 A Typical Oracle Real Application Clusters Guard Configuration

Oracle Real Application Clusters Guard can be deployed with MSCS on any Microsoft cluster system that meets the requirements of the Microsoft hardware compatibility list and the Oracle Real Application Clusters compatibility list.

Most clusters are configured similarly, differing only in choice of storage interconnect (SCSI or Fibre Channel) and in the way applications are deployed across the cluster nodes.

A typical cluster configuration includes the following hardware and software:

• Hardware
  • Microsoft cluster nodes, each with one or more local (private) disks.

  • Private (heartbeat) interconnect between the nodes for intracluster communications.

  • Public interconnect (internet, intranet, or both) to the local area network (LAN) or wide area network (WAN).

  • NTFS formatted disks on the shared storage interconnect (SCSI or Fibre Channel).

    Note: See the documentation for your cluster hardware for information on using redundant hardware, such as RAID, to further ensure high availability.

  • Raw partitions on the shared storage interconnect (SCSI or Fibre Channel) for Oracle Real Application Clusters databases. The data, log, and control files for each Oracle Real Application Clusters database instance are stored on a raw disk partition.

  • Additional redundant components (UPS, network cards, disk controllers, and so on).

• Software (installed on a private disk on each cluster node)
  • Windows NT Enterprise Edition, Windows 2000 Advanced Server, or Windows 2000 Datacenter Server

  • Oracle Real Application Clusters

  • Oracle Real Application Clusters Guard (Oracle Services for MSCS component)

  • Oracle Real Application Clusters Guard Manager (installed on one or more cluster nodes, one or more client workstations, or both)

See the Oracle Real Application Clusters Guard Release Notes for information about the supported releases of these components.

Figure 1-6 shows the hardware and software components in a two-node cluster configured with Oracle Real Application Clusters Guard. Note that the executable application files are installed on a private disk on each cluster node, the quorum resource (installed with MSCS) is on a shared-nothing NTFS disk, and the application data and log files for the Oracle Real Application Clusters database reside on shared raw disk partitions.

Figure 1-6 Hardware and Software Components in the Configuration

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