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