Welcome to my presentation of RMAN, the Recovery Manager. Recovery Manager (RMAN) is the component of the Oracle Database 10g used to perform backup, restore and recovery operations. Recovery Manager has a command line interface. Oracle Enterprise Manager also provides a graphical user interface for the Recovery Manager to the most commonly used functionality. Recovery Manager Features: Backup the database, tablespaces, data files, control files, and archived redo logs Manage backup and recovery tasks Perform incremental block-level backup and block-level media recovery Detect corrupted blocks during backup Use binary compression when creating backups RMAN provides several features not available when you make user-managed backups with operating system commands: Store frequently executed operations as scripts in the database. With block change tracking enabled in the database RMAN can limit incremental backups to recording only those blocks that have changed since the previous backup. This improves the performance of backups and may also reduce the time it takes to perform recovery operations in ARCHIVELOG mode. Manage the size of backup pieces and save time by parallelizing the backup operation. Recover an individual corrupt data block or set of data blocks within a data file rather than restoring and recovering the entire data file. RMAN operations can be integrated with the Oracle Database Scheduler to automate backup operations. Recovery Manager Components Enterprise Manager Database Control Console: Supplies a graphical interface to the most commonly used RMAN functionality. Server Session: The server process (UNIX) or threads (Windows NT/2000) invoked by RMAN connect to the target database to perform the backup, restore and recovery functions through a PL/SQL interface. These sessions read or write files to or from disk, tape or the Flash Recovery Area, a storage location specified as the default storage area for files related to database recovery. Target Database: Database for which backup and recovery operations are being performed using RMAN. The control file of the target database contains information about its physical structure, such as the size and location of data files, online and archived redo log files and control files. This information is used by the server sessions in backup and recovery operations. Auxiliary Database: Is used when creating a duplicate database or performing tablespace point-in-time recovery (TSPITR). Can reside on the same host as its parent or on a different host. Channel: Is a link to the database to perform and record backup and recovery operations. You can allocate channels manually or preconfigure channels using automatic channel allocation. RMAN Repository: Is to maintain metadata about the target database and its backup and recovery operations. Data is always stored in the control file of the target database. Recovery Catalog: RMAN repository data can optionally be kept in a recovery catalog which is a separate database that keeps historical data concerning backup activities much longer than the control file and preserves backup information if the control file is lost. A single recovery catalog can store information for multiple target databases. Can also hold RMAN stored scripts which are sequences of RMAN commands for common backup tasks. Usage of a separate recover catalog database is not recommended for small businesses where installation and administration of a separate recovery catalog database would be burdensome. Media Management Library: When writing to or reading from tapes. The additional media management software required for using the tape medium is provided by media and storage system vendors. Using a Flash Recovery Area with RMAN The Flash Backup and Recovery feature simplifies managing disk space and files related to backup and recovery by managing all backup and recovery related files in the Flash Recovery Area. RMAN generates file names for the backup files automatically. RMAN automatically uses Oracle Managed Files (OMF) for the backup files. Each time RMAN creates a file in the Flash Recovery Area, the Oracle Database updates a list of files that are no longer required on disk. When file needs to be written and no space available then Oracle Database deletes a file that is on the obsolete files list and writes a notification to the alert log. When space pressure or low free space because there are no files that can be deleted then a warning is issued. To resolve problem you can add disk space, backup your files to a tertiary device, delete the files from the Flash Recovery Area using RMAN or change the RMAN retention policy. By default, RMAN automatically backups files into a Flash Recovery Area when you set the DB_RECOVERY_FILE_DEST initialization parameter. Setting Parameters for RMAN RMAN stores information about the target database and its backup and recovery operations in the RMAN repository. The amount of information stored can increase depending on the frequency of backups, the number of archived redo log files that are generated and the retention period for RMAN records. The CONTROL_FILE_RECORD_KEEP_TIME parameter specifies the minimum number of days RMAN information is stored in the control file before being overwritten. The default is seven days. You can set the Flash Recovery Area size and location using the DB_RECOVERY_FILE_DEST and DB_RECOVERY_FILE_DEST_SIZE initialization parameters. You can also specify a retention policy that dictates when backups may be discarded. The NLS_DATE_FORMAT and NLS_LANG environment variables determine the format used for the time parameters in RMAN commands such as RESTORE, RECOVER and REPORT. Connection Types with RMAN You can use Recovery Manager to connect to the following types of databases: Target database: connected with SYSDBA privilege to perform typical RMAN operations. Recovery catalog database: optional database which is configured for the RMAN repository. To retrieve information such as backup information or stored scripts. Auxiliary database: created with the RMAN DUPLICATE command. Is a temporary database that is used during tablespace point-in-time recovery (TSPITR). Is a standby database or copy of the production database that can be used for disaster recovery. Starting RMAN For local RMAN connection at an operating system prompt, enter following. If you do not specify a user ID or password when connecting to the target database then a forward slash establishes a connection as user SYS by using operating system authentication. To connect from another server remotely, use the Oracle Net service name for the target database. Configuring Persistent Settings for RMAN You can use the CONFIGURE command to configure persistent settings for RMAN backup, restore, duplication and maintenance jobs. These settings are in effect for any RMAN session until the configuration is cleared or changed. Control File Autobackups To avoid losing a copy of the current control file, you should configure RMAN to take automatic backups of the control file. By default the control file autobackups are turned off. Control file autobackups are stored in the Flash Recovery Area, if configured. Retention Policies Recovery window: Establishes a period of time during which it will be possible to discover logical errors and fix the affected objects by doing a point-in-time recovery to just before the error occurred. This policy is specified in number of days. Redundancy: Establishes a fixed number of backups that must be kept. Backups that are in excess of this can be deleted. The value of the retention policy is set by the CONFIGURE command. Managing Persistent Settings The RMAN SHOW command allows you to view the RMAN configuration settings. You can return to the default value of any CONFIGURE command by running the same command with the CLEAR option. Channel Allocation A channel represents one stream of data to a device type. A channel must be allocated before you execute backup and recovery commands. Each allocated channel establishes a connection from the RMAN executable to a target database instance. An Oracle Database process for the target database is created for every channel allocated. Automatic and Manual Channel Allocation The CONFIGURE command is used to preconfigure channels for use in all RMAN sessions using automatic channel allocation. Automatic channels apply to any RMAN job in which you do not manually allocate channels. The ALLOCATE CHANNEL command with a RUN command issued at the RMAN prompt is used to allocate a channel manually. Manual channel allocation overrides automatic allocation. RMAN Command Overview The typical RMAN commands that you run against the target database include: - BACKUP: a database, tablespace, data file (current or copy), control file (current or copy), SPFILE, archived log or backup set for a target or standby database. Backing up backup set is an easy way to move a backup from disk to tape. - DUPLICATE: to create a clone database or a standby database from backups (backup sets or image copies) of the target database. - FLASHBACK: to perform a Flashback Database operation, returning the database to (or to just before) a target time, as specified by time, SCN or log sequence number. RMAN reporting commands include: - LIST: querying the recovery catalog or control file and producing a list of the backups, copies, archived redo logs and database incarnations recorded there. - REPORT: for performing detailed analyses of the recovery catalog or control file. - RMAN provides the following command sets for catalog maintenance: - CROSSCHECK: checks the status of a backup or a copy on disk or tape. - DELETE EXPIRED: lists specified backup objects and prompts for confirmation to remove them. - CHANGE: is used to alter the status of backup objects in the repository. - LIST: shows what CROSSCHECK / DELETE EXPIRED will process. RMAN Commands RMAN has two basic types of commands: stand-alone and job commands. Stand-alone commands are executed at the RMAN prompt and are generally self- contained. Job commands are usually grouped and executed sequentially inside of a command block. If any command within the block fails, RMAN ceases processing; no further commands within the block are executed. There are some commands that can be issued either at the prompt or within a RUN command block, such as BACKUP DATABASE. Job Command: Example Unlike stand-alone commands, job commands must appear within the brackets of a RUN command. The Backup Command A backup is a copy of data from the database that can be used to reconstruct that data. The results of an backup created through RMAN can be either image copies or backup sets. An image copy is a bit-for-bit identical copy of a database file. RMAN can also store its backups in an RMAN-exclusive format called a backup set which is a collection of files called backup pieces. When performing a backup using RMAN, you can specify: The type of backup to be performed. You can perform backups of the entire database (FULL) or incremental backups (INCREMENTAL). If CONFIGURE CONTROLFILE AUTOBACKUP is enabled, RMAN automatically backs up the control file and the current server parameter file after BACKUP commands. What to backup. Valid values are database, datafile, tablespace, archivelog, current controlfile or spfile. Whether an image copy (AS COPY) or backup set (AS BACKUPSET) is created. The file name format and location for backup pieces (FORMAT). Which data files or archived redo logs should be excluded from the backup set (SKIP). A maximum size for a backup set (MAXSETSIZE). That the input files should be deleted upon the successful creation of the backup set (DELETE INPUT). Compressed Backups Compressed backups reduce the amount of space required for storing backup sets. The compression applies only to backup sets, not image copies. RMAN can be configured to automatically make compressed backup sets with the CONFIGURE DEVICE TYPE command. By default compression is disabled. The Parallelism means that RMAN parallelizes its operation and writes multiple backup sets in parallel. Image Copy As mentioned before an image copy is a clone of a single file, archived redo log or control file. It can be created with the BACKUP AS COPY command or with an OS command. An image copy has the following characteristics: Can be written only to disk. If files are stored on disk, they can be used immediately by using the SWITCH command in Recovery Manager. In an image copy all blocks are copied, whether they contain data or not. Can be part of a full or incremental level 0 backup because a file copy always includes all blocks. Incremental Backups An incremental backup is either a level 0 backup which includes every block in the data files except blocks that have never been used or a level 1 backup which includes only those blocks that have been changed since a previous backup was taken. A level 0 incremental backup is physically identical to a full backup. The only difference is that the level 0 backup can be used as the base for a level 1 backup, but a full backup cannot. A cumulative level 1 incremental backup backs up all blocks changed after the most recent backup at level 0. A differential level 1 incremental backup , the default type of incremental backup, backs up all the blocks changed after the most recent incremental backup at either level 1 or level 0.
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