Database Reference
In-Depth Information
Summary
This chapter presented the main components of an Enterprise Manager Cloud Control system—Oracle Management
Service, Oracle Management Repository, Oracle Management Agent, and Software Library—that need to be
configured for high availability. Each of these components needs to be protected by using a different method.
Repository database high availability requires the use of database high-availability features including ASM, RAC,
and Data Guard. Each should be configured using Oracle-recommended best practices where appropriate. RAC
provides scalability and protects against the failure of a single host with seamless failover. Data Guard protects against
host and storage failure with minimal downtime (typically less than a minute) during role changes. In its most highly
configurable form, the repository database is deployed on a RAC database with a local RAC physical standby using
Data Guard. A standby site with identical configuration is also available to provide services in the event of a loss of the
primary site.
The Oracle Management Service can use various techniques to enable high availability, each differing in cost
and complexity. The simplest technique involves separating the OMS host from the repository host. You also looked
at an active/passive, or cold, failover solution in which multiple hosts share a single OMS on a shared filesystem, with
only one active at any given point in time. This uses the concept of a VIP to enable failover in the event of the loss of
one host in the cluster. Manual failover is required, and some downtime occurs as the OMS is restarted on another
host. The next level sets up multiple management services behind a load balancer. This enables a seamless failover
solution in the event of the loss of a single OMS. In an MAA configuration, a standby site is configured with a similar
configuration as the primary site. This obviously costs the most. However, it not only offers single-site availability but
also protects against disasters.
Management agents are made highly available by configuring reference images in the software library. This
makes the agents easier to recover using deployment procedures.
A key aspect of highly available architecture is its backup and recovery strategy. Each component in the
Enterprise Manager Cloud Control system should follow recommended best practices where appropriate to ensure
recoverability to meet business recovery point and recovery time objectives thus causing minimal disruptions to
the business.
In addition to the four levels of high availability discussed in this chapter, other technology solutions can provide
varying levels of high availability. These include but are not limited to virtualization software such as Oracle VM
Server, data replication technology including Oracle GoldenGate and Oracle Streams, and storage-level replication
solutions. The choice of a solution hinges on business requirements, resources, and costs.