Oracle HA: Harnessing the High Availability of Oracle Database（oracleha）
Oracle High Availability (HA) is a concept designed to ensure the availability and integrity of critical business data. Oracle Database HA offers a variety of technologies for both mission critical deployment and service continuity. It provides users with the infrastructure and capabilities required to reduce the effect of any unplanned outages and minimize downtime risks.
Oracle HA employs the service-oriented architecture (SOA) to build and manage availability of services. It is based on the three main layers that are responsible for the reliability and availability of services. These layers are:
1. Availability Strategy: This layer includes the planning, capability assessment, and implementation of measures that aid in the implementation of a well-developed and highly available system. It involves identifying priority of components, assess the failure risks, and select the right components for the system.
2. Hosts: This layer provides the physical environment within which the services run. It includes the hardware, operating system, storage, and uptime utilities that enable the system to remain available and undetected even if a particular component fails.
3. Services: This layer ensures that the service remains available, regardless of the failure of its underlying components. It does this by distributing the service’s tasks among multiple redundant hosts. All the tasks for service execution are executed in parallel and simultaneously by different fault-tolerant hosts.
The Oracle HA architecture, in a nutshell, works by spreading out the service’s tasks among multiple redundant hosts. This allows the system to remain available, even if a particular component fails. In the case of Oracle Database HA, the redundancy involves a master and a slave database. The master database handles write requests, while the slave database handles read requests. The tables in both databases are synchronized and passively replicated between the two servers to keep them in sync.
The replication is slowly and regularly done and is automatic. There are certain parameters that are set and must be followed while replicating the databases. The performance of the databases is duly monitored and evaluated by the Oracle Database HA system. If any discrepancies are found, the system will mark the replication process as failed and the databases as inconsistent.
The results from a properly running Oracle HA system are higher levels of system throughput and increased data transaction reliability. Additionally, the system can be configured to provide faster recovery in the event of a failure or data loss. The Oracle High Availability architecture can also be implemented in conjunction with other technologies to provide the most reliable system possible.
