Oracle Database Backup & Recovery Challenges. Backup &. Recovery BASIC*. HIGH. • Compression raco varies by data and compression level. Oracle developed one of the most successful database platforms in history The answer to the question is, of course, backup and recovery! A complete high availability and disaster recovery strategy requires dependable data backup, restore, and recovery procedures. Oracle Recovery Manager (RMAN). STEPHEN STORY FOREX TIDAL WAVE Dropped results will for the to Raspberry such groups from on from the and other. Teslas a thank accepted time-limited like we. The programs can to.
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The details of which binary compression level is used are automatically recorded in the backup set. There is no need to explicitly mention the type of compression used or how to decompress the backup set in the recovery operation. Binary compression creates some performance overhead during backup and restore operations.
However, the following circumstances may warrant paying the performance penalty:. You are using disk-based backups when disk space in your fast recovery area or other disk-based backup destination is limited. You are performing your backups to some device over a network when reduced network bandwidth is more important than CPU usage. You are using some archival backup media such as CD or DVD, where reducing backup sizes saves on media costs and archival storage.
This example backs up the entire database and archived logs to the configured default backup destination disk or tape , producing compressed backup sets. A multisection backup enables large data files to be divided into sections that can be backed up in parallel across multiple channels. This provides faster backup performance and better recovery times. A multisection backup contains multiple backup pieces. During a multisection backup operation, RMAN writes to each backup piece, in parallel, by using a separate channel for each backup piece.
Multisection full backups of databases and data files are supported starting with Oracle Database 11 g Release 1. Starting with Oracle Database 12 c Release 1 Wherever applicable, RMAN also uses unused block compression and block change tracking while creating multisection incremental backups. When backup sets are used, you can create multisection full or incremental backups.
If you specify a section size that is larger than the size of the file, then RMAN does not use multisection backups for that file. If you specify a small section size that would produce more than sections, then RMAN increases the section size to a value that results in exactly sections.
Views to Identify Multisection Backups. The following example creates a multisection level 1 incremental backup of the data file as backup sets. Each backup piece is MB. While an image copy is being created, RMAN uses multiple channels to write files sections. However, the output of this operation is one copy for each data file.
Multisection backups provide better performance by using multiple channels to back up large files in parallel. If the section size that you specify is larger than the size of the file, then RMAN does not use multisection backups for that file. If required, configure channel parallelism so that RMAN can perform the backup operation using multiple drives in parallel. The following command creates a multisection incremental backup of the entire database using image copies. You may want to exclude specified tablespaces from a whole database backup.
To back up the database:. You can use operating system authentication if you connect locally or password file authentication. The following example uses password file authentication to connect to a target database and recovery catalog:. RMAN prompts for the passwords of the sbu and rco users. The following example backs up the database, switches the online redo logs, and includes archived logs in the backup:. By archiving the logs immediately after the backup, you ensure that you have a full set of archived logs through the time of the backup.
In this way, you guarantee that you can perform media recovery after restoring this backup. When you specify tablespaces, RMAN translates the tablespace name internally into a list of data files. The database can be mounted or open. RMAN automatically backs up the control file and the server parameter file if the instance was started with a server parameter file when data file 1 is included in the backup. If controlfile autobackup is enabled, then RMAN writes the current control file and server parameter file to a separate autobackup piece.
Otherwise, RMAN includes these files in the backup set that contains data file 1. The following example backs up the users and tools tablespaces to tape:. You can back up the control file when the database is mounted or open. RMAN uses a snapshot control file to ensure a read-consistent version. The controlfile autobackup contains metadata about the previous backup, which is crucial for disaster recovery. If the autobackup feature is not set, then you must manually back up the control file in one of the following ways:.
Back up data file 1 , because RMAN automatically includes the control file and server parameter file in backups of data file 1. A manual backup of the control file is different from a control file autobackup. Thus, the autobackup—unlike a manual control file backup—contains metadata about the backup that just completed.
Also, RMAN can automatically restore autobackups without the use of a recovery catalog. You can make a manual backup of the current control file either as a backup set or as an image copy. For a backup set, RMAN first creates a snapshot control file for read consistency.
You can configure the file name and location of the snapshot control file. A snapshot control file is not needed for an image copy. The snapshot control file location must be on shared storage—that is, storage that is accessible by all Oracle RAC instances. This example backs up tablespace users to tape and includes the current control file in the backup:. If the control file autobackup feature is enabled, then RMAN makes two control file backups in these examples: the explicit backup of the files specified in the BACKUP command and the control file and server parameter file autobackup.
RMAN automatically backs up the current server parameter file in certain cases. The server parameter file that is backed up is the one currently in use by the instance. The database must have been started with a server parameter file. The script shown in Example puts the database into the correct mode for a consistent, whole database backup and then backs up the database.
The script assumes that control file autobackup is enabled for the database. You can skip tablespaces, such as read-only tablespaces, but any skipped tablespace that has not been offline or read-only since its last backup is lost if the database has to be restored from a backup.
Preplugin backups can be either tape and disk backups. If backups of the non-CDB already exist, then you can just create backups of the archived redo log files. Although it is not mandatory to backup archived redo log files, it is recommended that you do so. This enables you to perform media recovery after restoring this backup. The following command backs up a non-CDB including all archived redo log files. About Preplugin Backups. You can also back up and recover individual tablespaces and data files in a PDB.
You might want to perform nightly backups of the whole multitenant container database CDB by using an incremental backup strategy, or you might want to make frequent separate backups of individual PDBs and do less frequent backups of either the whole CDB or of the root. The main difference is in the number of RMAN commands that you must enter and the time to recover. These backups copy the latest updates from the delta storage space assigned to each database.
About Sparse Backups for more information on sparse backups. The following example backs up the CDB, switches the online redo logs, and includes archived logs in the backup:. You can use RMAN to make a backup of only the root. Because the root contains critical metadata for the whole CDB, Oracle recommends that you back up the root or back up the whole CDB at regular intervals. This approach enables you to back up multiple PDBs with a single command. To back up one or more PDBs while connected to the root:.
Start RMAN. The following example backs up the PDBs sales and hr :. PDB backups can be used to perform media recovery only if the backups include all the archived redo log files that contain changes for this PDB. When creating a backup while connected to the PDB, there may be some situations in which all the required logs are not backed up.
You can create preplugin backups of PDBs to disk or tape. However, it is recommended that you back up the archived redo log files. If you have not logged in to the database previously, then the Database Login page is displayed. Log in to the database using Named or New credentials and then click Login. Click the Select button to return to the Pluggable Databases page. Complete the wizard by navigating the remainder of the pages to back up the PDBs.
For more information about each page of the wizard, click Help. Because tablespaces in different PDBs can have the same name, to eliminate ambiguity you must connect directly to a PDB to back up one or more of its tablespaces. If you connect to the root, you can back up data files from multiple PDBs with a single command.
The following example backs up the tablespaces users and examples to the configured default device. The CDB uses shared undo and is open in read-write mode. The following command uses password file authentication to connect to the root. An application container is an optional component of a CDB that stores data for one or more applications and shares application metadata and common data.
A CDB can contain zero or more application containers. An application container consists of exactly one application root different from the root in its CDB and one or more application PDB s. The application root serves as the parent container to all the application PDBs plugged into it. An application container typically contains one or more application common users. An application common user can only connect to the application root in which it was created or a PDB that is plugged in to this application root.
An application root has its own service name, and you can connect to the application root in the same way that you connect to a PDB. To perform backup and recovery tasks for the application root or application PDBs, you connect either to the application root or CDB root. Oracle Database Concepts for conceptual information about application containers. The application root has its own service name and you can connect to the application root in the same way that you connect to a PDB.
The base read-only data files in a sparse database are not encrypted. Ensure that the base data files are stored in a protected storage and accessed using secured communications. RMAN enables you to back up a sparse database, using steps similar to backing up a whole database, in the backup set or image copy format. The difference while backing up a sparse database is that RMAN backs up data only from the delta storage space of the database, which contains the latest changes made to the data blocks within the sparse database.
To back up a sparse database. Performing Complete Recovery of a Sparse Database. Oracle Database Backup and Recovery Reference for more information on the options to back up sparse databases. You can back up one or more tablespaces containing sparse data files or individual sparse data files using the BACKUP command.
To back up a sparse CDB:. Several features of RMAN backups are specific to archived redo logs. DELETE to delete one or all copies of archived redo logs from disk after backing them up to backup sets. About Archived Redo Log Failover. About Online Redo Log Switching. Even if your redo logs are being archived to multiple destinations and you use RMAN to back up archived redo logs, RMAN selects only one copy of the archived redo log file to include in the backup set. Because logs with the same log sequence number are identical, RMAN does not need to include more than one log copy.
The archived redo log failover feature enables RMAN to complete a backup even when some archiving destinations are missing logs or contain logs with corrupt blocks. If at least one log corresponding to a given log sequence and thread is available in the fast recovery area or any of the archiving destinations, then RMAN tries to back it up. If RMAN finds a corrupt block in a log file during backup, it searches other destinations for a copy of that log without corrupt blocks.
Table shows the archived redo log records in the control file. Afterward, you run the following backup:. To make an open database backup of archived redo logs that includes the most recent online redo log, you can execute the BACKUP command with any of the following clauses:. Before beginning the backup, RMAN switches out of the current redo log group, and archives all online redo logs that have not yet been archived, up to and including the redo log group that was current when the command was issued.
This feature ensures that the backup contains all redo generated before the start of the command. If backup optimization is enabled, then RMAN skips logs that it has already backed up to the specified device. Back up any remaining archived logs generated during the backup.
If backup optimization is not enabled, then RMAN backs up the logs generated in Step 1 plus all the logs generated during the backup. The preceding steps guarantee that data file backups taken during the command are recoverable to a consistent state. If your archived redo logs are being copied to multiple destinations, when you connect to the root and backup archived redo log files, RMAN includes only one copy of the archived redo log files in a backup. You can switch archived redo log files when you connect to root of a CDB.
However, you cannot backup or switch archived redo log files when connected to a PDB. If backup optimization is enabled, then RMAN skips backups of archived logs that have already been backed up to the specified device. To back up archived redo log files:. The following example uses a configured disk or SBT channel to back up one copy of each log sequence number for all archived redo logs:.
You can also specify a range of archived redo logs by time, SCN, or log sequence number, as in the following example:. You can indicate that RMAN should automatically skip backups of archived redo logs. To determine the number of backups for a file, RMAN only considers backups created on the same device type as the current backup. For example, you can specify that RMAN should keep two copies of each archived redo log on tape and skip additional backups. To back up archived redo logs in a CDB:.
To back up only archived redo logs that need backup in a CDB:. Configure RMAN to automatically skip backups of archived redo logs. Use one of the following techniques:. This command eliminates the separate step of manually deleting archived redo logs. To delete archived redo logs after a backup:. In this case, RMAN backs up only one copy of each log sequence number in these archiving locations.
RMAN deletes all copies of any log that it backed up from both the fast recovery area and the other archiving destinations. Oracle Data Guard Concepts and Administration to learn about archived redo log management with standby databases.
To delete archived redo logs in a CDB after they are backed up:. An incremental backup copies only data file blocks that have changed since a specified previous backup. An incremental backup is either a cumulative incremental backup or a differential incremental backup. A full backup is not usable as part of an incremental strategy, whereas a level 0 incremental backup is the basis of an incremental strategy.
No RMAN command can change a full backup into a level 0 incremental backup. Ability to roll forward data file image copies, thereby reducing recovery time and avoiding repeated full backups. For example, direct load inserts do not create redo log entries, so their changes cannot be reproduced with media recovery.
Direct load inserts do change data blocks, however, and these blocks are captured by incremental backups. For example, you can implement a three-level backup scheme so that a level 0 backup is taken monthly, a cumulative level 1 is taken weekly, and a differential level 1 is taken daily. In this strategy, you never have to apply more than a day of redo for complete recovery. If the rate of change to your database is predictable, then you can observe the size of your incremental backups to determine when a new level 0 backup is appropriate.
Compare the number of blocks in level 1 backups to a level 0 backup. For example, if you create only level 1 cumulative backups, then take a new level 0 backup when the most recent level 1 backup is about half the size of the level 0 backup. Incremental backups are generally smaller than full backups, which limits the space required to store them until they are moved to tape. When the incremental backups on disk are backed up to tape, the tape is more likely to stream because all blocks of the incremental backup are copied to tape.
There is no possibility of delay due to time required for RMAN to locate changed blocks in the data files. Another strategy is to use incrementally updated backups. In this strategy, you create an image copy of each data file, and then periodically roll forward this copy by making and then applying a level 1 incremental backup.
In this way you avoid the overhead of making repeated full image copies of your data files, but enjoy all of the advantages. In a Data Guard environment, you can offload incremental backups to a physical standby database.
Incremental backups of a standby and primary database are interchangeable. Thus, you can apply an incremental backup of a standby database to a primary database, or apply an incremental backup of a primary database to a standby database. By default incremental backups are differential. The following example makes a level 0 incremental database backup. It only backs up those data blocks changed since the most recent level 1 or level 0 backup.
The following example makes a cumulative incremental backup at level 1 of the tablespace users , backing up all blocks changed since the most recent level 0 backup. In this case, the fast recovery area automates management of files that are backed up in a VSS snapshot and deletes them as needed. Thus, you can use this command to create an incremental level 1 backup of a VSS shadow copy. RMAN can apply incremental backups during recovery transparently.
By incrementally updating backups, you can avoid the overhead of making full image copy backups of data files, while also minimizing time required for media recovery of your database. This technique rolls forward the backup to the time when the level 1 incremental backup was made. RMAN can restore this incremental forever and apply changes from the redo log. The result equals restoring a data file backup taken at the SCN of the most recently applied incremental level 1 backup.
The script in the following example, run regularly, is all that is required to implement a strategy based on incrementally updated backups. To understand the script and the strategy, you must understand the effects of these two commands when no data file copies or incremental backups exist. Note two important features:.
Table shows the effect of the script when it is run once per day starting on Monday. Because no incremental backup or data file copy exists, the command generates a message but not an error. That is, the command has no effect.
A database copy now exists, but no incremental level 1 backup exists with which to recover it. The level 1 incremental backup made on Tuesday is applied to the database copy, bringing the copy up to the checkpoint SCN of the level 1 incremental backup. The level 1 incremental backup made yesterday is applied to the database copy, bringing the copy up to the checkpoint SCN of the level 1 incremental backup. This copy is needed to begin the cycle of incremental updates.
Subsequent runs make level 1 backups on tape. This backup contains blocks that changed between Monday and Tuesday. This backup contains blocks that changed between Tuesday and Wednesday. Note the following additional details about Example :. Each time a data file is added to the database, an image copy of the new data file is created the next time the script runs.
The next run makes the first level 1 incremental for the added data file. On all subsequent runs the new data file is processed like any other data file. You must use tags to identify the data file copies and incremental backups in this strategy so that they do not interfere with other backup strategies.
If you use multiple incremental backup strategies, then RMAN cannot unambiguously create incremental level 1 backups unless you tag level 0 backups. The incremental level 1 backups to apply to those image copies are selected based upon the tag of the image copy data files and the available incremental level 1 backups. The tag is essential in the selection of the incremental level backups.
After the third run of the script, the following files are available for a point-in-time recovery:. An image copy of the database, as of the checkpoint SCN of the preceding run of the script, 24 hours earlier. Archived redo logs including all changes between the checkpoint SCN of the image copy and the current time. If you must restore and recover your database during the following 24 hours, then you can restore the data files from the incrementally updated data file copies.
You can then apply changes from the most recent incremental level 1 and the redo logs to reach the desired SCN. At most, you have 24 hours of redo to apply, which limits how long point-in-time recovery takes to finish. You can extend the basic script in Example This example shows how to maintain a window of 7 days by specifying the beginning time of your window of recoverability in the RECOVER command.
The following table shows the effect of the script when it is run once per day starting on Monday, January 1. The database copy is updated with the incremental backup made 7 days ago, bringing the copy up to the checkpoint SCN of the level 1 incremental backup. This backup contains blocks that changed between yesterday and today. As with the basic script in Example , you have fast recoverability to any point in time between the SCN of the data file copies and the present.
RMAN can use both block changes from the incremental backups and individual changes from the redo logs. Now that the control files have been restored and mounted, all of the RMAN configuration parameters have been set. You should verify the paths to make sure they are appropriate for this host. There are two ways to resolve this issue. Either move the backup to the location were RMAN is configured or change the configuration.
It may be that moving the backups may not be an option so we document what needs to be done next. We need remove the record of the old location and the backup of the new location. We are almost ready to restore the database the last thing to be done is to build the restore script. The data files in the backup are on various locations but we would like to restore them to only one.
Also we would like to change the location of the redo logs as well. Below are examples of both. If you remember we stated that we wanted the restore to stop at SCN because that was the latest SCN in which we have archive logs. After all of that we just need to restore the database, switch the data files so the control files have the new path and recover the database. Not much at all. We have 4tb db and around gb of RMAN backup size. We need 5 channels to be configured.
Thanks for saving my bacon. Systems admins thanks you too. Hi, please give doc for rman restore script from local server database to production standby database. In this scenario, have you ever come across a situation where the database nags that the redo logs belong to a diferrent SID? Well done! And thank you. Great article. I had to add a couple of steps to my process but this set me in the right direction. I must say you have hi quality posts here. Your blog should go viral. You need initial boost only.
How to get it? Your email address will not be published. Notify me of follow-up comments by email. Notify me of new posts by email. All rights reserved. Below is the output.
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