| of nodes, networks, application services, EMS resources, and makes failover decisions based on |
| where the application is able to run successfully. |
cluster alarm | Time at which a message is sent indicating that the cluster is probably in need of recovery. The |
| cmrecoverclcommand is enabled at this time. |
cluster alert | Time at which a message is sent indicating a problem with the cluster. |
cluster event | A cluster condition that occurs when the cluster goes down or enters an UNKNOWN state, or |
| when the monitor software returns an error. This event may cause an alert messages to be sent |
| out, or it may cause an alarm condition to be set, which allows the administrator on the Recovery |
| Cluster to issue the cmrecovercl command. The return of the cluster to the UP state results in |
| a cancellation of the event, which may be accompanied by a cancel event notice. In addition, |
| the cancellation disables the use of the cmrecovercl command. |
cluster quorum | A dynamically calculated majority used to determine whether any grouping of nodes is sufficient |
| to start or run the cluster. Cluster quorums prevent |
| corruption or inconsistency. Currently at least 50% of the nodes plus a |
| for a quorum. If no |
| start and run a cluster. |
command device | A disk area in the HP StorageWorks P9000 Disk Array family or HP StorageWorks XP Disk Array |
| series disk array used for internal system communication. You create two command devices on |
| each array, each with alternate links (PV links). |
complex workload | Complex workloads are applications that are configured using multiple |
| that are managed collectively |
consistency group | A set of Symmetrix RDF devices that are configured to act in unison to maintain the integrity of |
| a database. Consistency groups allow you to configure R1/R2 devices on multiple Symmetrix |
| frames in Metrocluster with EMC SRDF. |
Continentalclusters |
|
| A group of clusters that use routed networks and/or common carrier networks for data replication |
| and cluster communication to support package failover between separate clusters in different |
| data centers. Continentalclusters are often located in different cities or different countries and can |
| span 100s or 1000s of kilometers. |
Continuous Access | A facility provided by the Continuos Access software option available with the HP StorageWorks |
| P9000 Disk Array family, HP StorageWorks E Disk Array XP series. This facility enables physical |
| data replication between P9000 or XP series disk arrays. |
D |
|
data center | A physically proximate collection of nodes and disks, usually all in one room. |
data consistency | Whether data are logically correct and immediately usable; the validity of the data after the last |
| write. Inconsistent data, if not recoverable to a consistent state, is corrupt. |
data currency | Whether the data contain the most recent transactions, and/or whether the replica database has |
| all of the committed transactions that the primary database contains; speed of data replication |
| may cause the replica to lag behind the primary copy, and compromise data currency. |
data loss | The inability to take action to recover data. Data loss can be the result of transactions being |
| copied that were lost when a failure occurred, |
| as pat of a recovery process, data in the process of being replicated that never made it to the |
| replica because of a failure, transactions that were committed after the last tape backup when a |
| failure occurred that required a reload from the last tape backup. transaction processing monitors |
| (TPM), message queuing software, and synchronous data replication are measures that can |
| protect against data loss. |
data mirroring | See See mirroring.. |
data recoverability | The ability to take action that results in data consistency, for example database rollback/roll |
| forward recovery. |
data replication | The scheme by which data is copied from one site to another for disaster tolerance. Data replication |
| can be either physical (see physical data replication) or logical (see logical data replication). In |
| a Continentalclusters environment, the process by which data that is used by the cluster packages |
516 Glossary