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# Glossary

24x365

24 hours a day, 365 days a year.

active/active configuration

A cluster configuration in which all cluster nodes perform work. If one node becomes unavailable, then one or more other nodes take over the workload of the node that is no longer available.

active/passive configuration

A cluster configuration in which one node usually stands idle in anticipation of a failover from another node.

availability

The measure of the ability of a system or resource to provide the desired service when required. Availability is measured in terms of the percentage of time the device is accessible out of the total time it is needed. Businesses that require uninterrupted computing services have an availability goal of 24x365.

bequeath protocol

A protocol that enables clients to retrieve information from an Oracle database without using the network listener. The bequeath protocol internally spawns a server thread for each client application. In a sense, it does the same operation that a remote network listener does for a database connection, but locally.

CGI

See common gateway interface (CGI).

client application

The application that provides all user-oriented activities, such as character or graphical user display, screen control, data presentation, application flow, and other application-specific tasks.

cluster

A group of two or more independent computing systems that operate as a single virtual system.

cluster alias

A node-independent network name that identifies a cluster and is used for cluster-related system management.

cluster node

A Windows system that is a member of a cluster.

cluster resource

A resource that is configured and managed on a cluster node. See also resource and standalone resource.

common gateway interface (CGI)

Part of a Web server that allows user interaction, typically using a Web browser, with programs running on the server. CGI scripts enable this user interaction to create dynamic Web pages or Web page elements, or to take user input and respond accordingly. A very common use is to provide an interactive form that a user completes online and then submits. Some common languages in use for CGI scripts are Perl, JavaScript, and Java.

data file

A file that contains the contents of logical database structures, such as tables and indexes. One or more data files form a logical unit of storage called a tablespace. A data file can be associated with only one tablespace, and only one database.

downtime

The measure of the inability of a system or resource to provide the desired service when required. Downtime is measured in terms of the percentage or amount of time the device is not accessible out of the total time it is needed.

failback

The process of intentionally returning a group of cluster resources to a preferred owner node from the failover node after the preferred owner node returns to operational status.

failback policy

See group failback policy.

failover

The process of taking cluster resources offline on one node and bringing them back online on another node. This process can either be planned (for upgrades and maintenance, for example) or unplanned (due to system or resource failure, for example).

failover node

The server node that takes over the workload of an unavailable node.

failover period

A user-specified time period in which the cluster software must continue to try to move cluster resources from one node to another before discontinuing the failover process and taking the resources offline. See also group failover policy.

failover policy

See group failover policy or resource failover policy.

failover threshold

The maximum number of times the cluster software must attempt to move resources from one node to another during the time period (failover period) that you specify. After reaching the specified failover threshold, the cluster software will stop the failover process and take the resources offline. See also group failover policy.

fail-safe resource

A resource that has been configured for high availability.

failure

The inability of a computing component to perform its function correctly.

generic service

A Windows service that is supported by the generic service resource DLL provided with Microsoft Cluster Server (MSCS). The generic service resource DLL is used to configure standard Windows services (such as IP addresses, physical disks, and some applications) as resources in a cluster.

group

A logical collection of cluster resources that forms a minimal unit of failover. In a failover situation, the group of resources is moved together to a failover node. A group resides on only one cluster node at a time.

group failback policy

A user-specified plan that determines when and if cluster resources must fail back to the preferred owner node from the failover node.

group failover

The process of taking a group of cluster resources offline on one node and attempting to bring them back online on another node. This process can either be planned (for upgrades and maintenance, for example) or unplanned (due to system or resource failure, for example).

group failover policy

A user-specified plan that determines two parameters: the time period in which the cluster software must continue to move resources from one node to another (failover period), and the maximum number of times failover must occur during the failover period (failover threshold). See also failover period and failover threshold.

heartbeat connection

See private interconnect.

host name

A name that represents the specific IP address on a network. In Microsoft Cluster Server (MSCS), the host name is mapped to a network name resource. See also network name.

instance

A combination of System Global Area (SGA) and one or more Oracle database processes. When a database is started, Oracle allocates SGA and starts one or more Oracle processes. The memory and processes of an instance efficiently manage the associated database's data and serve the database users. Each instance has a unique Oracle System Identifier (`SID`), instance name, instance number, rollback segments, and thread ID.

internode network connection

See private interconnect.

IP address

The Internet Protocol (IP) address. An IP address takes the form n.n.n.n, for example, 138.2.134.113.

listener

A service that receives requests by clients and redirects them to the appropriate server.

Microsoft Cluster Server (MSCS)

Microsoft Corporation software that provides the capability to cluster individual nodes that are running supported Windows operating systems. See Oracle Fail Safe Release Notes for a list of the supported operating system releases.

mission-critical application

A type of business function that is critical to the company and requires high availability.

net service name

Network information that describes the network and connection data of an Oracle database. More than one net service name can be defined for an Oracle database.

network name

The Microsoft Cluster Server (MSCS) term for a NetBIOS name, which translates into a specific IP address on a network. See also host name.

node

A computing system that is a member of a cluster.

planned group failover

The process of intentionally taking client applications and cluster resources offline on one node and bringing them back online on another node. For example, the Oracle Fail Safe Installation Guide describes how to perform a planned failover to perform a rolling upgrade (you fail over all resources to one cluster node as you sequentially upgrade software or hardware on another node). See also unplanned group failover.

possible owner node

A node capable of running a specified resource based on the following qualities:

- The resource DLL for the specified resource has been installed on the node.

- The resource has been configured to run on the node.

- You have not manually removed the node from the possible owner nodes list for the resource or the group containing the resource.

In a two-node cluster, both nodes must be possible owner nodes for all resources in a group if you want that group to be able to fail over.

possible owner nodes list

The set of all nodes on which the resource DLL for the specified resource has been installed and configured to run, less any nodes that you explicitly remove from the set.

preferred owner node

The node on which you want a group to reside when all cluster nodes that are possible owners are up and running. See also failover node.

primary nodes

In an active/passive configuration, the nodes that perform work. See also active/passive configuration.

private interconnect

A network connection that is dedicated to intracluster communication. The private interconnect is also referred to as a heartbeat connection, because it allows one node to detect the availability or unavailability of another node. The private interconnect is distinct from the public interconnect. See also public interconnect.

public interconnect

A network connection (such as a LAN or WAN) that connects clients to the cluster. See also private interconnect.

quorum

A voting mechanism used to guarantee that specific data necessary for recovery can be maintained consistently among all cluster members. This mechanism involves a special storage resource called the quorum resource. The quorum is also used to establish the cluster. See also quorum resource.

quorum resource

The quorum-capable storage resource selected to maintain the configuration data necessary for recovery of the cluster. The quorum resource is generally accessible to other cluster resources so that any cluster node has access to the most recent changes to the configuration data. See also quorum.

redundant components

Duplicate or extra computing components that safeguard the integrity of a computing system.

reliability

The ability of a computing system to operate without failing.

resource

A physical or logical component that is available to a computing system. For example, a resource can be a disk, a network IP address, an Oracle database, or a listener. See also cluster resource and standalone resource.

resource dependencies

Relationships between resources in a group that define the order in which the cluster software brings those resources online and offline.

resource failover policy

A policy that specifies whether or not a resource failure must result in a group failover.

resource restart policy

A policy that specifies whether or not the cluster software must attempt to restart a failed resource on its current node, and if so, how many attempts within a given time period must be made to restart it.

rolling upgrade

A software installation technique that allows a cluster system to continue to provide service while the software is being upgraded to the next release. This process is called a rolling upgrade because each node is upgraded and restarted in turn, until all cluster systems and client nodes have been upgraded. While each node is temporarily offline, another node takes over the workload of the node being upgraded.

sample database

An optional, preconfigured starter database that is provided with Oracle Fail Safe so you can try out the functions of Oracle Fail Safe before using them on your production database.

secondary node

In an active/passive configuration, a node that stands by to accept the work of a primary node in case of a failover. See also active/passive configuration and primary nodes.

service name entry

See net service name.

shared-nothing configuration

A cluster configuration in which all cluster nodes are cabled physically to the same disks, but only one node can access a given disk at a time for either read or write activity.

shared storage interconnect

An I/O connection on which the cluster disks are accessible from all nodes in a cluster.

silent mode

An installation method that lets you install software by supplying input to Oracle Universal Installer with a response file.

standalone resource

A resource that is not contained in a group. A standalone resource is hosted by a specific cluster node. See also cluster resource and group.

standby node

A node in an active/passive architecture that is ready to pick up application processing if a preferred owner node fails. See also active/passive configuration and preferred owner node.

subnet mask

A 32-bit value that indicates how many bits in an address are being used for the network ID.

transparent application failover

The ability of client applications to automatically reconnect to a database and resume work after a failover occurs.

unplanned group failover

A software-initiated failover process that is triggered automatically in response to a software or hardware failure. See also planned group failover.

virtual address

A network address at which resources in a group can be accessed, regardless of the cluster node hosting those resources. A virtual address on an MSCS cluster consists of a network name and associated IP address.

virtual directory

A name that maps to a physical directory specification. You specify a virtual directory to hide your file structure from users. If the physical directory changes, then the URL specified by users does not change. For example, if your virtual address is `Company`, and you have mapped the virtual directory `Sales` to `U:\SalesInfo\Webfiles`, then users will access sales information by entering the URL `http://Company/Sales`.

virtual server

A group with one or more virtual addresses.