Oracle Essentials [Electronic resources] : Oracle Database 10g, 3rd Edition نسخه متنی

1.9 Database Management Features

Oracle includes many features that
make the database easier to manage. We've divided
the discussion in this section into four categories: Oracle
Enterprise Manager, add-on packs, backup and recovery, and database
availability.

1.9.1 Oracle Enterprise Manager

As part of every Database Server, Oracle provides the
Oracle Enterprise Manager (EM), a
database management tool framework with a graphical interface used to
manage database users, instances, and features (such as replication)
that can provide additional information about the Oracle environment.
EM can also manage Oracle's Application Server,
Collaboration Suite, and E-Business Suite.

Prior to the Oracle8i database, the EM software
was installed on Windows-based systems, each repository accessible by
only a single database manager at a time. EM evolved to a Java
release providing access from a browser or Windows-based system.
Multiple database administrators could then access the EM repository
at the same time.

More recently, an EM HTML console was released with
Oracle9iAS with
important new application performance management and configuration
management features. The HTML version supplemented the Java-based
Enterprise Manager earlier available. Enterprise Manager 10g,
released with Oracle Database 10g, also comes in Java and HTML
versions. EM can be deployed in several ways: as a central console
for monitoring multiple databases leveraging agents, as a
"product console" (easily installed
with each individual database), or through remote access, also known
as "studio mode." The HTML-based
console includes advanced management capabilities for rapid
installation, deployment across grids of computers, provisioning,
upgrades, and automated patching.

Oracle Enterprise
Manager 10g has several additional options (sometimes called packs)
for managing the Oracle Enterprise Edition database. These options,
which are available for the HTML-based console, the Java-based
console, or both, include:

Database Diagnostics option

Application Server Diagnostics option

Database Tuning option

Database Change Management option

Database Configuration Management option

Application Server Configuration Management option

Standard management pack functionality for managing the Standard
Edition is now also available for the HTML-based console.

1.9.1.1 EM2Go

EM2Go is a mobile
version of Enterprise Manager that provides a subset of the
functionality in EM. EM2Go is accessed through a Pocket PC browser on
a PDA device. Database management capabilities include alert
notification and viewing, job creation and scheduling, database
performance monitoring and status (including Top Sessions, locks, and
SQL assessment), basic storage administration, tablespace operations
management, and system configuration status. EM2Go also monitors
availability and performance of Oracle Application Servers.

1.9.2 Availability

While both the Java- and HTML-based consoles of Enterprise Manager
10g can be used for managing Oracle, functionality is different in
the two consoles. We discuss this further in Chapter 5. Oracle Application Server, Oracle E-Business
Suite, and Oracle Collaboration Suite are managed through the
HTML-based console.

1.9.3 Backup and Recovery

As every database administrator
knows, backing up a database is a rather mundane but necessary task.
An improper backup makes recovery difficult, if not impossible.
Unfortunately, people often realize the extreme importance of this
everyday task only when it is too lateusually after losing
business-critical data due to a failure of a related system.

The following sections describe some products and techniques for
performing database backup operations. We discuss backup and recovery
strategies and options in much greater detail in Chapter 10.

1.9.3.1 Recovery Manager

Typical backups include complete database backups (the most common
type), tablespace backups, datafile backups, control file backups,
and archived redo log backups. Oracle8 introduced the
Recovery Manager (RMAN) for the
server-managed backup and recovery of the database. Previously,
Oracle's Enterprise Backup Utility (EBU) provided a
similar solution on some platforms. However, RMAN, with its Recovery
Catalog stored in an Oracle database, provides a much more complete
solution. RMAN can automatically locate, back up, restore, and
recover datafiles, control files, and archived redo logs. RMAN, since
Oracle9i, can restart backups and restores and
implement recovery window policies when backups expire. The Oracle
Enterprise Manager Backup Manager provides a GUI-based interface to
RMAN. Oracle Enterprise Manager 10g introduces a new improved job
scheduler that can be used with RMAN and other scripts, and that can
manage automatic backups to disk.

1.9.3.2 Incremental backup and recovery

RMAN can perform incremental backups of Enterprise
Edition databases. Incremental backups back up only the blocks
modified since the last backup of a datafile, tablespace, or
database; thus, they're smaller and faster than
complete backups. RMAN can also perform point-in-time recovery, which
allows the recovery of data until just prior to an undesirable event
(such as the mistaken dropping of a table).

1.9.3.3 Oracle Storage Manager and Automated Disk Based Backup and Recovery

Various media-management software vendors support RMAN. Since
Oracle8i, a Storage Manager has come bundled
with Oracle to provide media-management services, including the
tracking of tape volumes, for up to four devices. RMAN interfaces
automatically with the media-management software to request the
mounting of tapes as needed for backup and recovery operations.

Oracle Database 10g
introduces Automated Disk Based Backup and Recovery. The disk acts as
a cache, and archives and backups can then be copied to tape. The
disk "cache" can also serve as a
staging area for recovery.

1.9.3.4 Availability

Backup and recovery facilities are available for both Oracle Standard
Edition and Enterprise Edition.

1.9.4 Database Availability

Database
availability depends upon the reliability and management of the
database, the underlying operating system, and the specific hardware
components of the system. Oracle has improved availability by
reducing backup and recovery times. It has done this through:

Providing online and parallel backup and recovery

Improving the management of online data through range partitioning

Leveraging hardware capabilities for improved monitoring and failover

The relevant features are described in the following sections.

1.9.4.1 Partitioning option

Oracle introduced
partitioning as
an option with Oracle8 to provide a higher degree of manageability
and availability. You can take individual partitions offline for
maintenance while other partitions remain available for user access.
In data warehousing implementations, partitioning is frequently used
to implement rolling windows based on date ranges.
Hash
partitioning, in which the data partitions are divided up as a result
of a hashing function, was added to Oracle8i to
enable an even distribution of data. You can also use
composite partitioning to enable
hash subpartitioning within specific range partitions.
Oracle9i added list partitioning, which enables
the partitioning of data based on discrete values such as geography,
and composite range-list.

1.9.4.2 Data Guard

Oracle first introduced a
standby
database feature in Oracle 7.3. The standby database provides a copy
of the production database to be used if the primary database is
lostfor example, in the event of primary site failure, or
during routine maintenance. Primary and standby databases may be
geographically separated. The standby database is created from a copy
of the production database and updated through the application of
archived redo logs generated by the production database.

Data
Guard, first introduced in
Oracle9i, fully
automates this process; previously, you had to manually copy and
apply the logs. Agents are deployed on both the production and
standby database, and a Data Guard Broker coordinates commands. A
single Data Guard command is used to run the eight steps required for
failover.

In addition to providing physical standby database support, Data
Guard can create a logical standby database. In this scenario, Oracle
archive redo logs are transformed into SQL transactions and applied
to an open standby database.

Oracle
Database 10g introduces several new features, including support for
real-time application of redo data, integration with the Flashback
database feature, and archive log compression. From Oracle Database
10g forward, rolling upgrades are supported.

1.9.4.3 Fail Safe

The Fail
Safe feature provides a higher level of reliability for an Oracle
database. Failover is implemented through a second system or node
that provides access to data residing on a shared disk when the first
system or node fails. Oracle Fail Safe for Windows, in combination
with Microsoft Cluster Services, provides a failover solution in the
event of a system failure.

Fail Safe is primarily a disaster recovery tool, so some downtime
does occur as part of a failover operation. The recommended solution
for server availability has been Real Application Clusters since
Oracle9i.

1.9.4.4 Oracle Real Application Clusters

The Oracle Parallel Server (OPS) option was
replaced by Real Application Clusters (RAC)
beginning with Oracle9i. RAC
can provide failover support as well as increased scalability on
Unix, Linux, and Windows clusters. Oracle8i OPS
greatly improved scalability for read/write applications
through the introduction of Cache Fusion.
Oracle9i RAC provided Cache Fusion for
write/write applications by greatly minimizing much of the disk write
activity used to control data locking. Oracle Database 10g introduces
a new level of RAC portability and Oracle support by providing
integrated "clusterware" for the
supported RAC platforms.

With Real Application Clusters, you can run multiple Oracle instances
on systems in a shared disk cluster configuration or on multiple
nodes of a Massively Parallel Processor (MPP) configuration. RAC is
also a key enabler for grid computing. RAC coordinates traffic among
the systems or nodes, allowing the instances to function as a single
database. As a result, the database can scale across dozens of nodes.
Because the cluster provides a means by which multiple instances can
access the same data, the failure of a single instance will not cause
extensive delays while the system recovers; you can simply redirect
users to another instance that's still operating.

1.9.4.5 Data Guard and RAC

Data
Guard and RAC in combination replaced Parallel Fail Safe beginning
with
Oracle9i.
Data Guard provides automated failover with bounded recovery time in
conjunction with Oracle Real Application Clusters. In addition, it
provides client rerouting from the failed instance to the instance
that is available with fast reconnect, and automatically captures
diagnostic data. With Oracle Database 10g and Enterprise Manager
Version 4, it is possible to manage Data Guard configurations
containing RAC primary and secondary databases implemented with
Oracle Database 10g's integrated clusterware.

1.9.4.6 Automated Storage Management

Oracle Database
10g introduces Automated Storage
Management (ASM), which provides optimum striping and mirroring of
data for performance and availability. Because disks can now be
optimally tuned via the database, ASM in Oracle Database 10g greatly
simplifies this critical management task.

1.9.4.7 Availability

Advanced high-availability features such as the Partitioning Option
and Real Application Clusters have typically been available for
Oracle Enterprise Edition but not for Standard Edition. Oracle Data
Guard is bundled with the Enterprise Edition.