Typically, a high availability solution provides redundancy in one data centre. Disaster recovery solutions provide the ability to safeguard against natural or unplanned outages at a production site by having a recovery strategy for applications and data to a geographically separate standby site.
With Oracle Weblogic 12.2.1, the new feature of Continuous Availability is included. Continuous availability is the ability of a system to provide maximum availability by employing both high availability and disaster recovery solutions to ensure that applications are available when they are needed. It provides an integrated solution for building Maximum Availability Architectures (MAA) that span data centres across distributed geographical locations.
Integrated components include:
- Oracle WebLogic Server
- Oracle Coherence
- Oracle Traffic Director
- Oracle Site Guard
The key features of continuous availability are as follows :
1) Active Active Availability
2) Reduced application downtime
3) Automated Data Centre setup/ Failover
This can be achieved through the following:
Cross Domain Transation recovery
- It provides automatic recovery of XA transactions across an entire domain, or across an entire site with servers running in a different domain or at a different site.
- requires TLogs to be configured
- relies on TLogs being replicated by database replication technology such asOracle Data Guard, for high availability
Multi-datacenter Federeated Caching
- This is a coherence feature, distributed coherence data across sites.
Replicates cache data asynchronously across multiple geographically distributed clusters.
- Supports multiple replication topologies such as active-active, active-passive, hub-spoke
Zero Downtime Patching
- It allows you to rollout distributed patches to multiple clusters or to your entire domain with a single command. All without causing any service outages or loss of session data for the end-user. For more details see link
Recoverable Persistent Caching
- Durable storage of cached data and metadata with automated recovery.
Data is persisted so that it can be quickly recovered after a catastrophic failure or after a cluster restart due to planned maintenance.
Multitenant live partition migration
- Migrates running tenant partitions that are running from one cluster/server to another within a domain without impacting users.
Eliminating application downtime for planned events.
Oracle Traffic Director (OTD)
- It is a fast, reliable, and scalable layer-7 software load balancer that you can deploy as the reliable entry point for all TCP, HTTP and HTTPS traffic to application servers and web servers in your network.
- It can can handle large volumes of application traffic with low latency.
- It can be grouped as pairs of Oracle Traffic Director instances for active-passive or active-active failover, can easily scale the environment by reconfiguring Oracle Traffic Director with additional back-end servers
- It can be configured to apply multiple, declarative rules when distributing requests to the back-end servers and when forwarding responses to clients.
Oracle Site Guard
- It is a part of Oracle Enterprise Manager,
- It provides flexible and seamless orchestration of switchovers and failovers between disaster recovery sites, minimizing downtime for enterprise deployments.
- It provides a means by which Oracle Commerce MAA can be maintained automatically with only a couple of steps.
- It pulls the error-prone human element out of the reconfiguration to ensure error-free changes.
- It also includes the ability to test the outcome of any changes before you need to commit them.
- It provides end-to-end Disaster Recovery automation by orchestrating coordinated failover of Oracle Fusion Middleware & Oracle Databases.
- It also helps in achieving graceful site level role transitions by reducing the possibility of human errors during Disaster Recovery coordination and by streamlining the end-to-end recovery during planned & unplanned events.
Continuous Availability provides flexibility by supporting different topologies to meet application needs.
- Active-Active Application Tier with Active-Passive Database Tier
- Active-Passive Application Tier with Active-Passive Database Tier
- Active-Active Stretch Cluster with Active-Passive Database Tier