Oracle Application Server 10g Essentials [Electronic resources] نسخه متنی

2.2 Oracle Application Server Infrastructure

Shadow processes such as
OPMN, DCM, and DMS, and configuration management tools such as Oracle
Enterprise Manager, depend on a repository of configuration data.
This repository is part of what is known as the Oracle
Application Server Infrastructure. The OracleAS
Infrastructure may consist of a simple file-based repository, or may
be as complex as a database repository with an LDAP server.

2.2.1 OracleAS Infrastructure Components

The
OracleAS Infrastructure is divided
into two parts:

OracleAS Metadata Repository

Holds
Oracle Application Server configuration information and other
component information in a collection of schemas

Oracle Identity Management

Contains several subcomponents that
work together to provide a seamless Single Sign-on facility

In addition, the Application Server Control tool and a group of
shadow processes can be considered a part of the overall OracleAS
Infrastructure.

2.2.1.1 OracleAS Metadata Repository

The OracleAS Metadata Repository is either operating system
file-based or an Oracle database. The Java Edition of
Oracle Application Server uses a file-based repository for DCM. The
Portal/Wireless Edition and the BI/Forms Edition always use an
OracleAS Metadata Repository in an Oracle database.

If Oracle Application Server is
clustered (a topic described later in this chapter) and a file-based
repository is being used, one of the clustered Oracle Application
Server instances is designated as a central
repository. This designation
isn't necessary if a database repository is being
used.

The OracleAS Infrastructure installation normally clones a new Oracle
database to use as a database repository. During the installation
process, it is possible to use an existing database instance for the
OracleAS Metadata Repository, instead of creating a new one. However,
specifying an existing instance has an impact on the use of the
OracleAS Backup and Recovery Tool, described in Chapter 3.

2.2.1.2 Oracle Identity Management

Oracle Identity Management is a term used with Oracle Application
Server 10g that encompasses all the components
used to support enterprise-style security in Oracle Application
Server. All these components depend on the OracleAS Metadata
Repository:

Oracle Internet Directory

Provides an LDAP directory for
security principals (login information)

Oracle Directory Provisioning Integration Service

Allows the LDAP directory to import
and replicate data between homogeneous or heterogeneous types of LDAP
servers

Oracle Delegated Administration Services

Allows regional administrators and users
to update directory information in the Oracle Internet Directory

OracleAS Single Sign-On

Supports the Single Sign-on capability
for all Oracle Application Server applications

OracleAS Certificate Authority

Provides
an infrastructure for
creating and maintaining SSL certificates

Chapter 4 describes Oracle Application Server
security in greater detail.

2.2.2 Application Server Control

The web-based Oracle Enterprise Manager 10g tool
used to monitor and control Oracle Application Server is known as
Application Server Control.
Application Server Control is actually
an Oracle Application Server application that is installed with the
OracleAS Infrastructure and with each individual application server
home. The tool has a graphical user interface and is used to manage
individual instances of Oracle Application Server. Other portions of
the overall Oracle Enterprise Manager
10g product handle management of the database
and a grid of computing resources.

Oracle Enterprise Manager stores component configuration data in the
Metadata Repository. Doing so simplifies the management for multiple
Oracle Application Server instances when Oracle Application Server
clusters are being used.

Chapter 3 describes Oracle Enterprise Manager
10g, Application Server Control, and Grid
Control, as well as other Oracle Application Server management tools,
in more detail.

2.2.3 Shadow Processes

Oracle Application Server has many different
components, and some deployment architectures may have more than one
instance of any one of these components. To keep the burden of
monitoring, managing, and coordinating the interaction between these
components from being too overwhelming, Oracle Application Server
includes three shadow processes, shown earlier in Figure 2-1:

Oracle Process Manager and Notification Server

Distributed Configuration Management

Dynamic Monitoring Service

These shadow processes also use the OracleAS
Metadata Repository. DCM updates component
configuration files so that they will match the values in the
repository. OPMN uses the repository to identify what components
should be started and monitored. DMS stores runtime statistics in the
repository.

2.2.3.1 Oracle Process Manager and Notification Server

The Oracle
Process Management and
Notification Server monitors the health of the individual components
in an Oracle Application Server architecture. OPMN monitors and
manages all Oracle Application Server components, with the exception
of the following:

The repository database, if used

The listener for the database

The Application Server Console

If a particular component becomes unavailable, OPMN automatically
restarts it. OPMN also informs any dependent component that a
component isn't available. For example, suppose that
a request for a Java application comes into an Oracle HTTP Server. It
is passed to the mod_oc4j module, which passes the
request to an OC4J process. If the OC4J process goes down, OPMN lets
the mod_oc4J process know that it should prevent
any additional requests from being routed to the failed process. In
this way, OPMN simplifies management while making the entire set of
Oracle Application Server components highly available.

2.2.3.2 Distributed Configuration Management

For high
availability and scalability, you can create
clusters of Oracle Application Server
components (Oracle HTTP Server and OC4J) and OracleAS Web Cache. The
Distributed Configuration Management service coordinates
configuration information across all members of a cluster.

DCM automatically replicates base configuration information to a new
member of a cluster. It also propagates changes to any of this
information to all members of a cluster. In addition to this base
information, each cluster member also has some individual
configuration parameters of its own, such as port numbers for the
instance.

You can also use DCM to make a backup of your configuration files
that can be used to restore these crucial files in the event of
corruption.

DCM is invoked through the Application Server Control tool or via the
dcmctl command-line tool.

2.2.3.3 Dynamic Monitoring Service

Oracle Application Server uses the Dynamic Monitoring Service
to collect information about the performance of some of its
components. DMS uses sensors to measure various types of durations or
simply the occurrence of different types of events. DMS periodically
collects the information from these sensors and compiles it into
metrics. You can access these metrics using a variety of different
tools. The most commonly used is dmstool, a
command-line tool for presenting DMS metrics. The metrics may also be
accessed in different portions of the Application Server Control
tool.

DMS sensors are built into Oracle Application Server
Containers for J2EE, so metrics are automatically provided for all
applications that run in an OC4J container. You can add sensors to
any application you deploy on Oracle Application Server through a DMS
API, so the use of DMS is completely extensible. You can also turn
off DMS to save the small amount of overhead incurred.