Database Reference
In-Depth Information
proves more trouble than it is worth due to the way it is implemented. When verifying the contents of the RPM you get
lots of missing files, which is not a defect but rather how that particular RPM is designed.
The agent has its own package and library prerequisites, which are usually met already when installing it on an
Oracle database server. The agent image will require 1 GB free hard disk space. Unlike Oracle Enterprise Manager 11.1
and earlier, you can no longer download the agent from Oracle's website. The agent has become an integral part of
Enterprise Manager and as such is internally managed via a new OEM 12c feature named “Self-Update”. You always
get the agent for your OMS platform as part of the installation. Management agents for other platforms need to be
downloaded from My Oracle Support.
Not
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You can find more information about how to configure and use self-Update later in this chapter.
The agent has been specifically created with a less-than-optimal network connectivity to the Management
Service in mind. It is able to tolerate network disconnects and poorly performing infrastructure without severely
impacting the Enterprise Management deployment as a whole. Although an unreliable communication between an
agent and the OMS will be felt for the targets monitored by the agent, it should not cause an effect that can be felt
system-wide.
High latencies and disconnects between the repository and Management Service however are poison to the
deployment of Enterprise Manager. The impact of poor network quality between the Management Host and the
repository database is severe and likely to be felt by every user connecting to the console.
The Oracle Management Service
The Oracle Management Service or OMS is at the heart of the Enterprise Manager infrastructure. Agents upload
their metric information to the OMS, and users connect to the Enterprise Manager console. Information, current
and historic, is available from the repository database at the application's backend. At its heart, the OMS is a Java
application using WebLogic as the execution environment. As such there are considerations about the amount of
memory and the number of CPU cycles available for users. Oracle documentation contains a lot of information on the
sizing of the OMS, and there is also a section about sizing considerations in the chapter you are reading. Although it
tries to list the main points, it cannot replace the official documentation so have a look at that as well.
You are not limited to having only one OMS, Enterprise Manager is built to scale out horizontally by adding more
OMSs to the configuration. For larger deployments it might be beneficial to add an optional load balancer into the
infrastructure (while at the same time not forgetting to take high availability precautions for the database). Instead
of communicating directly with an individual OMS the agents will communicate with the load balancer's IP address.
Since the load balancer is a perfect single point of failure, you should ensure with the network department that there
is resilience built into the design there too!
A lot of important functionality is available from the Cloud Control console, such as notifications and incident
management which are going to be covered later in the chapter.
The Enterprise Manager Repository
The repository database is the place where all the information gathered by agents throughout the estate is stored.
Not every database release is certified to act as a management repository. You should check the certification matrix
on My Oracle Support first. As a rule of thumb, if your release is still in premium support and Patch Set Updates
are produced, then there is a high probability that your database is indeed certified. You may have to wait a little
bit though for support of Oracle 12c as a repository database. Unlike some previous versions, the Oracle Universal
Installer does not create a database for you, and there is no option to install everything on the same host as in
Enterprise Manager 10g. Instead, you have to point the installer to an existing database.
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