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 Oracle9iAS and Oracle iFS, Internet Directory, and Express.
Prior to the Oracle8i database, the EM software had to be installed on Windows 95/98 or NT-based systems and each repository could be accessed by only a single database manager at a time. Now you can use EM from a browser or load it onto Windows 95/98/2000 or NT-based systems. Multiple database administrators can access the EM repository at the same time. In the EM release for Oracle9i, the super administrator can define services that should be displayed on other administrators’ consoles, and management regions can be set up.
Several optional add-on packs are available for Oracle, as described in the following sections and in more detail in Chapter 5. In addition to these database-management packs, management packs are available for Oracle Applications and for SAP R/3.
The Standard Management Pack for Oracle provides tools for the management of small Oracle databases (e.g., Oracle Server/Standard Edition). Features include support for performance monitoring of database contention, I/O, load, memory use and instance metrics, session analysis, index tuning, and change investigation and tracking.
You can use the Diagnostics Pack to monitor, diagnose, and maintain the health of Enterprise Edition databases, operating systems, and applications. With both historical and real-time analysis, you can automatically avoid problems before they occur. The pack also provides capacity planning features that help you plan and track future system-resource requirements.
With the Tuning Pack, you can optimize system performance by identifying and tuning Enterprise Edition database and application bottlenecks such as inefficient SQL, poor data design, and the improper use of system resources. The pack can proactively discover tuning opportunities and automatically generate the analysis and required changes to tune the system.
The Change Management Pack helps eliminate errors and loss of data when upgrading Enterprise Edition databases to support new applications. It can analyze the impact and complex dependencies associated with application changes and automatically perform database upgrades. Users can initiate changes with easy-to-use wizards that teach the systematic steps necessary to upgrade.
Oracle Enterprise Manager can be used for managing Oracle Standard Edition and/or Enterprise Edition. Additional functionality for diagnostics, tuning, and change management of Standard Edition instances is provided by the Standard Management Pack. For Enterprise Edition, such additional functionality is provided by separate Diagnostics, Tuning, and Change Management Packs.
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 late—usually 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 archivelog 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 for 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.
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 a undesirable event (such as the mistaken dropping of a table).
Various media-management software vendors support RMAN. Oracle bundles Legato Storage Manager 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.
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 to 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 adds list partitioning, which enables the partitioning of data based on discrete values such as geography.
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 lost—for 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. The Oracle9i Data Guard product 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, Oracle9i Data Guard (second release) will be able to create a logical standby database. In this scenario, Oracle archive logs are transformed into SQL transactions and applied to an open standby database.
The failover 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 NT/2000, in combination with Microsoft Cluster Services, provides a failover solution in the event of a system failure. Unix systems such as HP-UX and Solaris have long provided similar functionality for their clusters.
The Oracle Parallel Server (OPS) option, renamed Real Application Clusters in Oracle9i, can provide failover support as well as increased scalability on Unix and Windows NT clusters. Oracle8i greatly improved scalability for read/write applicationsthrough the introduction of Cache Fusion. Oracle9i improved Cache Fusion for write/write applications by further minimizing much of the disk write activity used to control data locking.
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. The Real Application Cluster coordinates traffic among the systems or nodes, allowing the instances to function as a single database. As a result, the database can scale across hundreds of nodes. Since 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. You can write applications with the Oracle Call Interface (OCI) to provide failover to a second instance transparently to the user.
Parallel Fail Safe, renamed RACGuard in Oracle9i, provides automated failover with bounded recovery time in conjunction with Oracle Parallel Server/Real Application Clusters. In addition, Parallel Fail Safe provides client rerouting from the failed instance to the instance that is available with fast reconnect and automatically captures diagnostic data.