8 i recovery_manager
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The document provides an overview of the technical features of Oracle8i Recovery Manager. Key features discussed include proxy copy which allows backups to be offloaded from the Oracle host to a media manager, disk affinity which improves backup performance, enhanced LIST and multiplexed backup set commands, automatic catalog maintenance, and point-in-time recovery of individual tablespaces to improve data availability. The Recovery Manager aims to provide improved ease of backup/recovery administration while maintaining high performance and database availability.
8 i recovery_manager
- 1. Oracle8iTM Recovery Manager Technical Features Overview February 1999 INTRODUCTION Database backup, restore and recovery are critical processes underlying any mission-critical system. Imagine the potential for lost revenue, customer dissatisfaction or unrecoverable information caused by a media failure or similar disaster. Long term projects, key customer information or new orders could be lost. A well-implemented data backup and recovery strategy is a cornerstone for every deployment, making it possible to restore and recover all or part of a database without data loss. With the release of Oracle8™ extensive backup and recovery functionality was added in a new utility. The Recovery Manager provided an integrated method for creating, managing and restoring backups of a database. Recovery Manager addresses the following requirements of a comprehensive database backup and recovery system: · Backing up a database must be performed without interrupting current business functions. · Recovery operations must be performed with minimal impact on the business processing. · Due to the large sizes of databases, backup sizes need to be proportional to the size of transactional changes on the system, not proportional to the size of the database itself. · Recovery time must be proportional to the amount of data being recovered. The objective in creating the Recovery Manager was to provide greater ease of management and administration of the backup and recovery operations while maintaining superior performance and increased availability of the database.
- 2. Oracle8i Recovery Manager February 1999 2 PRODUCT SUMMARY NEW RECOVERY MANAGER FUNCTIONALITY IN ORACLE8i Oracle8i, the database for Internet computing, builds on and adds to the Recovery Manager capabilities introduced with Oracle8. New Oracle8i Recovery Manager functionality includes: · Proxy Copy · Disk Affinity · LIST Command Enhancements · Recovery Catalog Cross Check · Multiplexed Backup Sets · Controlfile Character Set Specification · STARTUP and SHUTDOWN Commands · Clone Command · Automatic Catalog Maintenance PROXY COPY Recovery Manager controls the integration of the database server directly, using a tape media management system which is compliant with Oracle’s “System Backup to Tape (SBT)” tape media management application programming interface (API). This allows customers to choose from a variety of tape media management subsystems and enables Oracle to read or write tape volumes — perhaps in a tape library — directly. The Oracle8i server can integrate with any media management software that is compliant with Oracle's Media Management API. This allows customers to choose from a variety of tape media management subsystems, and enables Oracle to read or write backups on non-disk media such as tapes and to use automated tape libraries. In Oracle8i, the Media Management API has been enhanced to allow the bulk I/O of creating and restoring database backups to be off-loaded from the Oracle host to the media manager. This makes it possible, during full online or offline backups, for the Oracle database server to not be directly involved in the reading or writing process. Thus, media managers that directly integrate disk and tape storage subsystems can perform data movement between disk and tape at the speed of the underlying devices, freeing host CPU resources, and reducing the impact on application response time of backup or restore workloads.
- 3. This capability is known as "proxy copy" because Oracle selects the media manager as a proxy to actually copy data to or from tape and will be supported by a number of media management vendor partners in Oracle's Backup Solutions Program (BSP). Oracle8i Recovery Manager February 1999 3 DISK AFFINITY In Oracle® Parallel Server configurations, the speed of access to disks may not be uniform across the nodes of the cluster. One or more nodes may have "affinity" for a particular set of disks, which means that access to these disks from these nodes is more efficient than from other nodes. Recovery Manager in Oracle8i is aware of this affinity when scheduling backups and restores and attempts to schedule datafile backups on channels allocated at nodes that have affinity to those files. LIST COMMAND ENHANCEMENTS The LIST command in Oracle8i now supports multiple ListObjects, rather than just one. LIST BACKUPSET output has been enhanced to show backup pieces and files included in the set. The ALL keyword is added to list all backup sets in the catalog, whether usable by the current database incarnation or not. RECOVERY CATALOG CROSS CHECK A third-party media management subsystem often has its own catalog of backup files that maps a file to tape volumes and contains metadata about the backup files. Many media managers support automatic tape expiration. This can cause earlier versions of Recovery Manager’s recovery catalog to become out of sync with the backup file catalog. In Oracle8i, Recovery Manager provides a means to re-synchronize the recovery catalog with the media management catalog. MULTIPLEXED BACKUP SETS Archive logs are critical to data recovery and there should be redundant tape copies of each archive log. In Oracle8i, Recovery Manager provides an efficient way to create redundant archive log backup sets and datafile backup sets. A new command, “SET DUPLEX,” is used to specify how many copies of output files to create. Each channel will then create N copies of each backup piece, where N is the value specified in the SET DUPLEX command. If a tag is specified, then all backup pieces share the same tag.
- 4. Oracle8i Recovery Manager February 1999 4 CONTROLFILE CHARACTER SET SPECIFICATION Starting with Oracle Version 8.0.5, the database character set ID is stored in the controlfile. This allows access to the database character set before a database open — which is necessary for Recovery Manager to correctly interpret tablespace names prior to the database open when the character set happens to be something other than the default (US7ASCII). The CREATE CONTROLFILE syntax has been expanded to optionally accept the database character set name, so that character set information is available at mount time. STARTUP AND SHUTDOWN COMMANDS STARTUP and SHUTDOWN commands have been added to Recovery Manager for starting up and shutting down the target database. CLONE COMMAND The clone command enables the creation of a replicated database (clone) using the backups stored in the media manager from another database. This replicated database can be given a different DBNAME or have the same DBNAME as the one just cloned. One possible use of a clone database is to create a safe environment for testing backup and recovery procedures from a real, production database. AUTOMATIC CATALOG MAINTENANCE This feature allows recovery catalog creation and maintenance to be done via Recovery Manager commands rather than by running separate SQL scripts. The new commands are: CREATE CATALOG, UPGRADE CATALOG, and DROP CATALOG.
- 5. Oracle8i Recovery Manager February 1999 5 EXISTING RECOVERY MANAGER FUNCTIONALITY In addition to the new features listed above, Recovery Manager carries forward all the features and functionality introduced with Oracle8. One of the most important features is a backup and recovery process that is fully managed by the server. This not only greatly minimizes the likelihood of database administrator (DBA) error in the backup or recovery steps, it also frees the DBA from substantial administrative tasks. In other database management systems, the backup and restore operations are manual tasks with limited functionality, done at the operating system level, and the DBA has to spend considerable time managing this process. Restoring all or part of the database is very straightforward in Oracle8, because Recovery Manager finds the appropriate backups and restores them as needed. Recovery Manager automatically restores any archive logs needed for recovery as well. EASES MANAGEMENT OF THE BACKUP PROCESS Recovery Manager is the component of the backup and recovery system that manages backup creation, restoration and recovery operations. With Recovery Manager, database administrator productivity goes up and the frequency and severity of human errors goes down, because the database system is controlling and managing the backup and recovery operations. The work of actually creating backups and recovering with them is done inside the Oracle8i server itself. Recovery Manager maintains a recovery catalog that holds information about the backup files and archived redo log files, thereby freeing the DBA from having to track all the backup copies and archive logs. It then uses the recovery catalog to automate both restore and recovery operations, so there is no chance of accidentally restoring from the wrong backup. Recovery Manager provides a way to: · Automate Both the Restore and Recovery Operations. · Perform Automatic Parallelization of Backups and Restores. · Generate a Printable Report of All Backup and Recovery Activity. NO SINGLE POINT OF FAILURE Recovery Manager can maintain a recovery catalog containing information about the backup files and archived redo log files. This greatly simplifies backup management for the DBA, since the database system is now keeping track of all the backups. The recovery catalog minimizes the likelihood of administrator error, since the system determines which backups to restore from and which archive logs are needed to recover with that backup. The recovery catalog is used as a repository of information to automate both backup and restore operations, as well as recovery operations. Oracle8i can use one recovery catalog to manage multiple (local or remote) Oracle8i databases, thereby eliminating any possible single point of failure in the backup strategy.
- 6. The recovery catalog is stored in an Oracle8i database. The recommended approach is to use an alternate database to contain the recovery catalog for the target database being backed up. That way, a media loss on one database does not affect the recovery catalog, since it resides on a different database. For example, a production database can be backed up and managed with a recovery catalog that resides on a work station database, and that database can be backed up and managed with a recovery catalog that resides on the production database. This way, the workstation and production databases can provide comprehensive backup facilities for each other. It is critical that the recovery catalog be backed up also, to avoid any possibility of it being a single point of failure. It can then be backed up and recovered using the Oracle8i Recovery Manager facility, since it resides within an Oracle8i database. Larger sites with multiple Oracle8i systems installed may create a single recovery catalog to maintain backup and recovery information for all their Oracle8i databases. This greatly simplifies maintenance and administration of multiple databases. The recovery catalog can also be located at a remote site, separate from the target database or databases. This helps minimize the impact of any failure, since it is very unlikely that a recovery operation will be needed on the target database while there is a simultaneous failure of the remote recovery catalog database. The database server performs various integrity checks on the backup files used for a restore operation. Oracle8i Recovery Manager February 1999 6 COMPREHENSIVE REPORTS DESCRIBE BACKUP STATUS Reports can be run against the recovery catalog to see, for example, which files need backing up and which backups are no longer required. The recovery catalog contains: · Information About Datafile and Archivelog Backup Sets. · Information About Datafile Copies. · Information About Archived Redo Logs and Their Backup Copies. · Information About the Tablespaces and Datafiles of the Target Database. · Named User-Created Sequences of Commands Called Stored Scripts.
- 7. Oracle8i Recovery Manager February 1999 7 SIMPLIFIED FOR SMALL DATABASES The recovery catalog is optional in the backup and recovery strategy. Recovery Manager supports an operational mode where it obtains the recovery information needed from the control file. This mode is appropriate for small databases, where installation and administration of another database to serve as the recovery catalog would be burdensome, or in a case where the additional capabilities provided by the recovery catalog are not desired. Some features are not available when operating without a recovery catalog: · Point-In-Time Recovery · Stored Scripts · Automatic Recovery When the Control File Is Not Current BACKUP TYPES Oracle8i supports four basic methods of backups: · Backup Sets · Incremental Backups (Must Be Part of a Backup Set) · Datafile Copies · Operating System Generated Backups A backup set contains one or more input files of the same type, either datafiles or archive logs. This greatly simplifies backup file management, since multiple files may be backed up into one output file, so there are fewer files to store and manage. A particular backup file from the backup set must then be extracted with a restore operation by the Recovery Manager. Backup sets can be full or incremental backups of the files, taken while the database was open or closed. A backup is made up of one or more datafiles that contains all blocks of the datafile that have ever been used. Oracle8i allows you to create and restore full backups of datafiles, tablespaces, archive logs, control files — and the database in its entirety — for maximum manageability and flexibility. An incremental backup is a backup of one or more datafiles that contains only those blocks (at the same or a lower level), that have been modified since a previous backup. File size of backups is greatly reduced, since only modified blocks need to be backed up, instead of all blocks of the datafiles. Oracle8i allows you to create and restore incremental backups of datafiles, tablespaces, and the database. A datafile copy contains a single input datafile that can be used “as is” to perform recovery. No restore operation is needed to use it, thereby saving the time normally needed to restore the file. Sites that require true high availability benefit from this feature, because it allows the system to become available for work as quickly as possible. This type of file is created by Recovery Manager as a "fuzzy" copy of a single file, taken (if desired)
- 8. while the database is online and being updated. Simply point the control file directly at the backup copy and media recovery is performed to make the copy current. This type of backup is only allowed to disk, so the copy can be used "as is," without a restore operation. The recovery catalog is then updated to indicate that the copy has been "consumed;" in other words, the file copy is no longer available for any future use as a backup. Not having to restore the backup file saves a great deal of time, thereby making the recovered data available faster. The only additional downtime needed is the time required to do the actual recovery operation on that backup file. Operating system-generated backups created externally to Oracle are fully supported and usable under Oracle8i and may be tracked by the recovery catalog as a full, level 0 backup that can be used as a basis for subsequent incremental backups. Oracle8i Recovery Manager February 1999 8 AVAILABILITY INCREASES WITH INCREMENTAL BACKUP AND RESTORE The time it takes for backup and restore operations is relative to the amount of transactional data changed, and not to the size of the datafiles themselves. This substantially reduces the time needed to take backups of very large datafiles, since there is no need to copy the entire file. Once a baseline level 0 backup has been taken, subsequent backups need only copy the changed portions of the datafiles, rather than copying the whole file whether or not any data has been modified. These types of backups are called incremental backups. Incremental backups are taken as part of a backup set. It contains a backup of one or more datafiles that contains only those blocks that have been modified since a previous backup at the same or lower level. The multi-level incremental backup feature allows you to create different levels of incremental backups. Each level is indicated by an integer, with level 0 being used to backup all used datafile blocks. An incremental backup at any particular level consists of those blocks that have been modified since the last backup at that level or lower. Creating cumulative incremental backups reduces the work needed for a recovery operation. These backups ensure that you need only one incremental backup from any particular level at recovery time. However, cumulative backups require more space and time to create because they duplicate the work done by previous backups at the same level. REDUCES BACKUP AND RECOVERY TIME WITH PARALLEL OPERATIONS When backing up multiple datafiles, Recovery Manager automatically reads them in parallel. It is important to keep an output device streaming continuously, helping minimize the time needed for the backup operation. Recovery Manager uses asynchronous I/O to read the files and write to the output devices, if the platform supports it. You can use I/O slaves to take advantage of this performance improvement even in platforms that don't support asynchronous I/O.
- 9. Multiple backup or recovery sessions can be executed concurrently. Recovery Manager may parallelize its operation, establishing multiple logon sessions and conducting multiple conversations in parallel. Concurrent sessions must operate on disjoint sets of database files. Parallelization of backup, copy, and restore commands is handled automatically by the Recovery Manager. Recovery Manager establishes one database connection to the target database for each sequential I/O device. The administrator only needs to specify a list of one or more sequential I/O devices, and the objects to be backed up, copied, or restored. Parallelism is exploited within the context of a single command. So, if copies of 10 datafiles are needed, it is better to issue a single COPY command that specifies all ten copies, instead of issuing ten separate copy commands. Oracle8i Recovery Manager February 1999 9 INCREASES AVAILABILITY WITH POINT-IN-TIME TABLESPACE RECOVERY With Oracle8i, you can perform a point-in-time recovery on a single tablespace, instead of taking the whole database back in time logically. This allows some applications to continue to operate while some other part of the database is being recovered, thereby allowing greater availability of the data. It is strongly recommended that this feature be used with the guidance of Worldwide Support, since it is possible that human error will cause database inconsistency when a tablespace point-in-time recovery is performed. EASES THE USE OF ADMINISTRATION TOOLS Oracle® Enterprise Manager supports all the Recovery Manager facilities and provides a graphical user interface (GUI) to make it easier to use the Recovery Manager commands. This helps save database administrator time. It also allows scheduling of backups during off-periods of the system. Backups can then be scheduled at night, when there may be less activity on the system. A number of third-party vendors are integrating their products to support the Recovery Manager capabilities of Oracle8i using GUI interfaces; these will make working with Recovery Manager's recovery processes easier and make handling backups to disk and tape easier at the operating system (O/S) level.
- 10. Oracle8i Recovery Manager February 1999 10 MEDIA MANAGEMENT SYSTEM INTERFACE Backing up files to tape is required in most backup scenarios. This minimizes expensive disk consumption and facilitates sending backups elsewhere for disaster recovery. Copying a sizable database to disk is prohibitively expensive in many cases. Backing up to tape is the reasonable alternative. Also, backup tapes of the database can then be sent to a secondary location for long term storage, so they are available in the event of a major failure at the primary site. Recovery Manager supports an application programming interface (API) for data movement between Oracle and other vendors' products. This provides the integration with tape management systems that is necessary for backup and recovery. In most cases, there is no need to invest in new media management software packages. Oracle8i's backup and recovery facilities interface with most existing media management packages.
- 11. Oracle Corporation World Headquarters 500 Oracle Parkway Redwood Shores, CA 94065 U.S.A. Worldwide Inquiries: +1.650.506.7000 Fax +1.650.506.7200 http://www.oracle.com/ Copyright © Oracle Corporation 1999 All Rights Reserved This document is provided for informational purposes only, and the information herein is subject to change without notice. Please report any errors herein to Oracle Corporation. Oracle Corporation does not provide any warranties covering and specifically disclaims any liability in connection with this document. Oracle is a registered trademark, and Oracle8i and Oracle8 are trademarks of Oracle Corporation. All other company and product names mentioned are used for identification purposes only and may be trademarks of their respective owners.