oracle backup and recovery
Content
Oracle Backup and Recovery
Created By: Saurabh Kulkarni
www.yogijicreations.com
Index
Backup and Need of it Different types of backup
Hot vs cold Full vs incremental Physical vs logical
User Managed backup RMAN Database recovery
Flashback Recovery
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User managed RMAN based
Backup
What do we mean by database backup ?
The process of periodically taking a copy of the database and log file (and possibly programs) onto offline storage media.
A backup is a copy of data.
www.yogijicreations.com
Need of taking backup
Instance Failures
instance shuts down without synchronizing all the database files to the same system change number (SCN) A few causes for instance failure:
A power outage A server hardware failure Failure of an Oracle background process Emergency shutdown procedures (intentional power outage or SHUTDOWN ABORT)
Solution :STARTUP Database and let Oracle automatically perform instance recovery using the online redo logs and undo data in the undo tablespace.
www.yogijicreations.com
Need of taking backup
User Error Failures
Inadvertently delete or modify data in tables or drop an index. the DROP TABLE command worked fine, but you really didn’t want to drop that table!
www.yogijicreations.com
Media Failures
The loss of one or more database files (Datafiles, Control files, redo log files) The database file can be lost or corrupted for a number of reasons:
Failure of a disk drive Failure of a disk controller Inadvertent deletion or corruption of a database file
www.yogijicreations.com
Different types of backup techniques
Hot or On-line Backups
backup of one or more database files while the database is open Inconsistent !!!
Mismatch in SCN SCN ( System change Number):
A stamp that defines a committed version of a database at a point in time.
Oracle assigns every committed transaction a unique SCN.
www.yogijicreations.com
Different types of backup techniques
In 24 X 7 environment Database should be in ARCHIVELOG mode
www.yogijicreations.com
Different types of backup techniques
Cold /offline Backup
Backing up the database when it is closed (shutdown state). Consistent
No need of recovery because the data is already consistent.
www.yogijicreations.com
Different types of backup techniques
Whole database backups Tablespace Backups Datafile Backups
www.yogijicreations.com
Different types of backup techniques
Full Backup Incremental Backup
Differential Incremental Backup Cumulative Incremental Backup
www.yogijicreations.com
Differential Incremental Backup
Backup all the blocks that have changed between level 0 and level 1
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Cumulative Incremental Backup
Backup all the blocks till the level 1.
www.yogijicreations.com
User-Managed Backups
The basic user-managed backup strategy is to make periodic backups of datafiles and archived logs with operating system commands.
Logical or physical. Physical: Backup of physical file structure (datafiles, control files..) Logical: backups of logical objects such as tables, views…
Export / Import utility is used to take logical backup and restore it back.
www.yogijicreations.com
Basic Backup Methodology
Identify the datafiles, control files, and archived redo logs to be backed up by querying dynamic performance views or data dictionary tables Use an operating system command such as the UNIX cp command to back up datafiles and archived redo logs Use a SQL statement to back up the control file Use an operating system command such as the UNIX cp command to back up configuration files
www.yogijicreations.com
Basic Backup Methodology
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The RMAN
Oracle provided utility for backing-up, restoring and recovering Oracle Databases Doesn't require a separate installation. Off-line and on-line database backups. Can not write directly to tape.
3rd-party tools (like Veritas, Omiback) can integrate with RMAN to handle tape library management.
Only compatible with Oracle release 8.0 or higher
www.yogijicreations.com
www.yogijicreations.com
RMAN features
Compress backups of datafiles so that only those data blocks that have been written to are included in a backup Store frequently executed backup and recovery operations in scripts. Perform incremental backups Create a duplicate production database for testing purpose printable message log of all backup and recovery operations. Recovery catalog automates both restore and recovery operations Perform crosschecks
www.yogijicreations.com
RMAN Backup Concepts
Server-managed backup Can back up entire database, all datafiles in a tablespace, selected datafiles, control files, archived redo log files
www.yogijicreations.com
www.yogijicreations.com
RMAN: Backup techniques
Image File
Datafile 3 Control file Archived Log file Datafile 3
Copy of datafile 3 Copy of control file
Control file
Archived Log file Copy of archived log
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RMAN: Backup techniques
Backup Set
Datafile 1 Datafile 2 Datafile 3
Datafile 4 Control file
Datafile 1 Datafile 2
Datafile 3
Control file
Datafile 4
Backup set 1
Backup set 2
Backup set 3
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Backup Set
Usually contain more than one file. Can be written to a disk or tape. Required to extract files for restoration Can be incremental or full. Do not include never-used blocks.
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Backup Piece
A backup piece is a file in a backup set. A backup piece can contain blocks from more than one datafile.
Backup set 1 (Logical) Piece 1 (file) Piece 2 (file)
Datafile 1 Datafile 4 Datafile 5
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RMAN commands
BACKUP Back up database files, archive logs, backups, or copies. CATALOG Add information about files to the repository. (10g+) CHANGE Update the status of a backup in the RMAN repository. CONFIGURE Persistent RMAN settings. CONNECT Connect to a recovery catalog or auxiliary database CROSSCHECK Check whether backup items still exist. DELETE Delete backups from disk or tape EXIT Exit the RMAN console LIST List backups and copies
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RMAN Commands
RECOVER Apply redo logs or incremental backups to a restored backup set (or copy) in order to update it to a specified time. REPORT Report backup status: database, files, backups RESTORE Restore files from an RMAN backup (or copy) RUN Some RMAN commands are only valid inside a RUN block. SET Settings for the current RMAN session. SHOW Display the current configuration SHUTDOWN Shutdown the database SQL Execute a PL/SQL procedure or SQL statement(not SELECT) STARTUP Startup the database ADVISE FAILURE Display repair options (11g Data Recovery Advisor) REPAIR FAILURE Repair database failures (11g Data Recovery Advisor)
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Backing up database using RMAN
Command: Backup During an RMAN backup, the Oracle database server reads the datafiles, not an operating system utility. The server reads each block and determines whether the block is inconsistent. If the block is inconsistent, then Oracle rereads the block until it gets a consistent picture of the data.
www.yogijicreations.com
Backing up database using RMAN
Logical name assigned to a backup set or image copy
month_full_backup
Datafiles 1,3
Datafiles 2,4
week_full_backup Wednesday_1_backup
Datafile 3 Datafile 4 Datafile 1
Backup set
Backup set
Backup set
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RMAN Control File Autobackups
CONFIGURE CONTROLFILE AUTOBACKUP
When enabled, RMAN automatically performs a control file autobackup after BACKUP or COPY commands
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Archived Redo Log Backups Archived redo logs are essential for recovering an inconsistent backup. BACKUP ARCHIVELOG
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RMAN Dynamic Views
V$ARCHIVED_LOG V$BACKUP_CORRUPTION V$COPY_CORRUPTION V$BACKUP_DATAFILE V$BACKUP_REDOLOG V$BACKUP_SET V$BACKUP_PIECE
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Database Recovery
Difference between restoring and recovering? Restoring: copying backup files from secondary storage (backup media) to disk. Recovering: process of applying redo logs to the database to roll it forward.
www.yogijicreations.com
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Preparing to recover (user managed recovery)
Remain calm and do not panic Restore database files to their respective locations Recover the database to the point of failure using Online redo log files. (Roll forward) Roll back to the last consistent state.
www.yogijicreations.com
Restoring Backups of the Damaged or Missing Files
Determine which datafiles to recover
SELECT * FROM V$RECOVER_FILE;
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Restoring Backups of the Damaged or Missing Files
Query V$DATAFILE and V$TABLESPACE to obtain filenames and tablespace names for datafiles requiring recovery. Incase of media failure, indicate the new locations of datafiles files to the control file. If the database is open, then take the tablespaces containing the inaccessible datafiles offline.
ALTER TABLESPACE users OFFLINE IMMEDIATE; % cp /disk2/backup/tbs_24.bak /disk1/oracle/dbs/tbs_24.f
Copy backups of the damaged datafiles to their default location Recover the affected tablespace. RECOVER TABLESPACE users
Bring the recovered tablespace online
ALTER TABLESPACE users ONLINE
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Re-Creating Datafiles When Backups Are Unavailable
All archived log files written after the creation of the original datafile must be available The control file contains the name of the damaged file
Create a new, empty datafile to replace a damaged datafile that has no corresponding backup.
ALTER DATABASE CREATE DATAFILE '/disk1/users1.f' AS '/disk2/users1.f';
Perform media recovery on the empty datafile.
ALTER DATABASE CREATE DATAFILE '/disk1/users1.f' AS '/disk2/users1.f';
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Recovery of Database when Control files are lost
Find the location of the datafiles and log files. Create a new control file based on above information
CREATE CONTROLFILE REUSE DATABASE "ORCL10G" RESETLOGS LOGFILE GROUP 1 'K:\ORCL10G\LOG\REDO01.LOG' SIZE 50M, GROUP 2 'K:\ORCL10G\LOG\REDO02.LOG' SIZE 50M, DATAFILE 'K:\ORCL10G\DATA\SYSTEM01.DBF', 'K:\ORCL10G\DATA\UNDOTBS01.DBF', 'K:\ORCL10G\DATA\SYSAUX01.DBF‘;
Open the database with resetlogs option.
alter database open resetlogs;
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RMAN Recovery Techniques
Enhanced RMAN Features
Automated File Creation During Recovery Simplified Recovery Through Resetlogs Change-Aware Incremental Backups Automated Disk-Based Backup and Recovery RMAN Database Dropping and Deregistration
www.yogijicreations.com
Automated File Creation During Recovery
This feature enhances RMAN recovery by automatically creating and recovering datafiles that have never been backed up. Archive log files are still required
www.yogijicreations.com
Automated File Creation During Recovery
data file #1
data file #2
Missing data file #3
RMAN
Control fle
Archive log files
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Importance of Redo log files
The online redo logs are a set of two or more files that record
all changes made to Oracle datafiles and control files.
Whenever a change is made to the database, the Oracle database server writes the data and generates a redo record in the redo buffer
.
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Recovery using Flashback Functions
Flashback is an Oracle database facility to quickly move an entire database or a table back to a prior state for recovery purposes. Flashback was first introduced with Oracle 9i with Oracle's Flashback Query feature.
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FRA ( Flashback Recovery area)
storage area (directory on disk or ASM diskgroup) that enables database Flash Backup and Recovery operations. first introduced with Oracle 10g. Related parameters:
db_recovery_file_dest db_recovery_file_dest_size db_flashback_retention_target
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Flashback Query ( 9i Feature)
Allows users to see a consistent view of the database as it was at a point in the past.
In Oracle 10g, we can now retrieve all versions of the rows that exist or ever existed between the time the query was issued and a point back in time.
www.yogijicreations.com
Flashback Database
Faster than traditional point-in-time recovery. Traditional recovery method: Backups and Redo logs Flashback Database is implemented using a new type of log file called the Flashback Database log. Oracle database server periodically logs before images of data blocks in the Flashback Database logs. The data block images are used to quickly back out changes to the database during Flashback Database. RVWR: similar to the LGWR (log writer) process. writes Flashback Database data to the Flashback Database logs.
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Enabling Flashback Database
Make sure the database is in archive mode. Configure the recovery area by setting the two parameters: DB_RECOVERY_FILE_DEST DB_RECOVERY_FILE_DEST_SIZE Open the database in MOUNT EXCLUSIVE mode and turn on the flashback feature: SQL> STARTUP MOUNT EXCLUSIVE; SQL> ALTER DATABASE FLASHBACK ON; Set the Flashback Database retention target: DB_FLASHBACK_RETENTION_TARGET
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Flashback Drop
DROP command permanently removed objects from the database… In Oracle 10g, a DROP command places the object in the recycle bin. You can restore the object from the recycle bin at any time. Flashback table emp to before drop; drop table emp PURGE;
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Recycle Bin
A recycle bin contains all the dropped database objects until,
Permanently drop them with the PURGE command. Recover the dropped objects with the FLASHBACK TABLE command. There is no room in the tablespace for new rows or updates to existing rows. The tablespace needs to be extended.
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Flashback Table
Flashback Table allows you to recover a table or tables to a specific point in time without restoring a backup. When you use the Flashback Table feature to restore a table to a specific point in time, all associated objects, such as, indexes, constraints, and triggers will be restored. FLASHBACK TABLE emp TO SCN 76230;
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Flashback Transaction Query
It provides a way for you to view changes made to the database at the transaction level. It allows you to diagnose problems in your database and perform analysis and audit transactions
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Questions ?
For queries: [email protected]
www.yogijicreations.com
Created By: Saurabh Kulkarni
www.yogijicreations.com
Index
Backup and Need of it Different types of backup
Hot vs cold Full vs incremental Physical vs logical
User Managed backup RMAN Database recovery
Flashback Recovery
www.yogijicreations.com
User managed RMAN based
Backup
What do we mean by database backup ?
The process of periodically taking a copy of the database and log file (and possibly programs) onto offline storage media.
A backup is a copy of data.
www.yogijicreations.com
Need of taking backup
Instance Failures
instance shuts down without synchronizing all the database files to the same system change number (SCN) A few causes for instance failure:
A power outage A server hardware failure Failure of an Oracle background process Emergency shutdown procedures (intentional power outage or SHUTDOWN ABORT)
Solution :STARTUP Database and let Oracle automatically perform instance recovery using the online redo logs and undo data in the undo tablespace.
www.yogijicreations.com
Need of taking backup
User Error Failures
Inadvertently delete or modify data in tables or drop an index. the DROP TABLE command worked fine, but you really didn’t want to drop that table!
www.yogijicreations.com
Media Failures
The loss of one or more database files (Datafiles, Control files, redo log files) The database file can be lost or corrupted for a number of reasons:
Failure of a disk drive Failure of a disk controller Inadvertent deletion or corruption of a database file
www.yogijicreations.com
Different types of backup techniques
Hot or On-line Backups
backup of one or more database files while the database is open Inconsistent !!!
Mismatch in SCN SCN ( System change Number):
A stamp that defines a committed version of a database at a point in time.
Oracle assigns every committed transaction a unique SCN.
www.yogijicreations.com
Different types of backup techniques
In 24 X 7 environment Database should be in ARCHIVELOG mode
www.yogijicreations.com
Different types of backup techniques
Cold /offline Backup
Backing up the database when it is closed (shutdown state). Consistent
No need of recovery because the data is already consistent.
www.yogijicreations.com
Different types of backup techniques
Whole database backups Tablespace Backups Datafile Backups
www.yogijicreations.com
Different types of backup techniques
Full Backup Incremental Backup
Differential Incremental Backup Cumulative Incremental Backup
www.yogijicreations.com
Differential Incremental Backup
Backup all the blocks that have changed between level 0 and level 1
www.yogijicreations.com
Cumulative Incremental Backup
Backup all the blocks till the level 1.
www.yogijicreations.com
User-Managed Backups
The basic user-managed backup strategy is to make periodic backups of datafiles and archived logs with operating system commands.
Logical or physical. Physical: Backup of physical file structure (datafiles, control files..) Logical: backups of logical objects such as tables, views…
Export / Import utility is used to take logical backup and restore it back.
www.yogijicreations.com
Basic Backup Methodology
Identify the datafiles, control files, and archived redo logs to be backed up by querying dynamic performance views or data dictionary tables Use an operating system command such as the UNIX cp command to back up datafiles and archived redo logs Use a SQL statement to back up the control file Use an operating system command such as the UNIX cp command to back up configuration files
www.yogijicreations.com
Basic Backup Methodology
www.yogijicreations.com
www.yogijicreations.com
The RMAN
Oracle provided utility for backing-up, restoring and recovering Oracle Databases Doesn't require a separate installation. Off-line and on-line database backups. Can not write directly to tape.
3rd-party tools (like Veritas, Omiback) can integrate with RMAN to handle tape library management.
Only compatible with Oracle release 8.0 or higher
www.yogijicreations.com
www.yogijicreations.com
RMAN features
Compress backups of datafiles so that only those data blocks that have been written to are included in a backup Store frequently executed backup and recovery operations in scripts. Perform incremental backups Create a duplicate production database for testing purpose printable message log of all backup and recovery operations. Recovery catalog automates both restore and recovery operations Perform crosschecks
www.yogijicreations.com
RMAN Backup Concepts
Server-managed backup Can back up entire database, all datafiles in a tablespace, selected datafiles, control files, archived redo log files
www.yogijicreations.com
www.yogijicreations.com
RMAN: Backup techniques
Image File
Datafile 3 Control file Archived Log file Datafile 3
Copy of datafile 3 Copy of control file
Control file
Archived Log file Copy of archived log
www.yogijicreations.com
RMAN: Backup techniques
Backup Set
Datafile 1 Datafile 2 Datafile 3
Datafile 4 Control file
Datafile 1 Datafile 2
Datafile 3
Control file
Datafile 4
Backup set 1
Backup set 2
Backup set 3
www.yogijicreations.com
Backup Set
Usually contain more than one file. Can be written to a disk or tape. Required to extract files for restoration Can be incremental or full. Do not include never-used blocks.
www.yogijicreations.com
Backup Piece
A backup piece is a file in a backup set. A backup piece can contain blocks from more than one datafile.
Backup set 1 (Logical) Piece 1 (file) Piece 2 (file)
Datafile 1 Datafile 4 Datafile 5
www.yogijicreations.com
RMAN commands
BACKUP Back up database files, archive logs, backups, or copies. CATALOG Add information about files to the repository. (10g+) CHANGE Update the status of a backup in the RMAN repository. CONFIGURE Persistent RMAN settings. CONNECT Connect to a recovery catalog or auxiliary database CROSSCHECK Check whether backup items still exist. DELETE Delete backups from disk or tape EXIT Exit the RMAN console LIST List backups and copies
www.yogijicreations.com
RMAN Commands
RECOVER Apply redo logs or incremental backups to a restored backup set (or copy) in order to update it to a specified time. REPORT Report backup status: database, files, backups RESTORE Restore files from an RMAN backup (or copy) RUN Some RMAN commands are only valid inside a RUN block. SET Settings for the current RMAN session. SHOW Display the current configuration SHUTDOWN Shutdown the database SQL Execute a PL/SQL procedure or SQL statement(not SELECT) STARTUP Startup the database ADVISE FAILURE Display repair options (11g Data Recovery Advisor) REPAIR FAILURE Repair database failures (11g Data Recovery Advisor)
www.yogijicreations.com
Backing up database using RMAN
Command: Backup During an RMAN backup, the Oracle database server reads the datafiles, not an operating system utility. The server reads each block and determines whether the block is inconsistent. If the block is inconsistent, then Oracle rereads the block until it gets a consistent picture of the data.
www.yogijicreations.com
Backing up database using RMAN
Logical name assigned to a backup set or image copy
month_full_backup
Datafiles 1,3
Datafiles 2,4
week_full_backup Wednesday_1_backup
Datafile 3 Datafile 4 Datafile 1
Backup set
Backup set
Backup set
www.yogijicreations.com
RMAN Control File Autobackups
CONFIGURE CONTROLFILE AUTOBACKUP
When enabled, RMAN automatically performs a control file autobackup after BACKUP or COPY commands
www.yogijicreations.com
Archived Redo Log Backups Archived redo logs are essential for recovering an inconsistent backup. BACKUP ARCHIVELOG
www.yogijicreations.com
RMAN Dynamic Views
V$ARCHIVED_LOG V$BACKUP_CORRUPTION V$COPY_CORRUPTION V$BACKUP_DATAFILE V$BACKUP_REDOLOG V$BACKUP_SET V$BACKUP_PIECE
www.yogijicreations.com
Database Recovery
Difference between restoring and recovering? Restoring: copying backup files from secondary storage (backup media) to disk. Recovering: process of applying redo logs to the database to roll it forward.
www.yogijicreations.com
www.yogijicreations.com
Preparing to recover (user managed recovery)
Remain calm and do not panic Restore database files to their respective locations Recover the database to the point of failure using Online redo log files. (Roll forward) Roll back to the last consistent state.
www.yogijicreations.com
Restoring Backups of the Damaged or Missing Files
Determine which datafiles to recover
SELECT * FROM V$RECOVER_FILE;
www.yogijicreations.com
Restoring Backups of the Damaged or Missing Files
Query V$DATAFILE and V$TABLESPACE to obtain filenames and tablespace names for datafiles requiring recovery. Incase of media failure, indicate the new locations of datafiles files to the control file. If the database is open, then take the tablespaces containing the inaccessible datafiles offline.
ALTER TABLESPACE users OFFLINE IMMEDIATE; % cp /disk2/backup/tbs_24.bak /disk1/oracle/dbs/tbs_24.f
Copy backups of the damaged datafiles to their default location Recover the affected tablespace. RECOVER TABLESPACE users
Bring the recovered tablespace online
ALTER TABLESPACE users ONLINE
www.yogijicreations.com
Re-Creating Datafiles When Backups Are Unavailable
All archived log files written after the creation of the original datafile must be available The control file contains the name of the damaged file
Create a new, empty datafile to replace a damaged datafile that has no corresponding backup.
ALTER DATABASE CREATE DATAFILE '/disk1/users1.f' AS '/disk2/users1.f';
Perform media recovery on the empty datafile.
ALTER DATABASE CREATE DATAFILE '/disk1/users1.f' AS '/disk2/users1.f';
www.yogijicreations.com
Recovery of Database when Control files are lost
Find the location of the datafiles and log files. Create a new control file based on above information
CREATE CONTROLFILE REUSE DATABASE "ORCL10G" RESETLOGS LOGFILE GROUP 1 'K:\ORCL10G\LOG\REDO01.LOG' SIZE 50M, GROUP 2 'K:\ORCL10G\LOG\REDO02.LOG' SIZE 50M, DATAFILE 'K:\ORCL10G\DATA\SYSTEM01.DBF', 'K:\ORCL10G\DATA\UNDOTBS01.DBF', 'K:\ORCL10G\DATA\SYSAUX01.DBF‘;
Open the database with resetlogs option.
alter database open resetlogs;
www.yogijicreations.com
RMAN Recovery Techniques
Enhanced RMAN Features
Automated File Creation During Recovery Simplified Recovery Through Resetlogs Change-Aware Incremental Backups Automated Disk-Based Backup and Recovery RMAN Database Dropping and Deregistration
www.yogijicreations.com
Automated File Creation During Recovery
This feature enhances RMAN recovery by automatically creating and recovering datafiles that have never been backed up. Archive log files are still required
www.yogijicreations.com
Automated File Creation During Recovery
data file #1
data file #2
Missing data file #3
RMAN
Control fle
Archive log files
www.yogijicreations.com
Importance of Redo log files
The online redo logs are a set of two or more files that record
all changes made to Oracle datafiles and control files.
Whenever a change is made to the database, the Oracle database server writes the data and generates a redo record in the redo buffer
.
www.yogijicreations.com
Recovery using Flashback Functions
Flashback is an Oracle database facility to quickly move an entire database or a table back to a prior state for recovery purposes. Flashback was first introduced with Oracle 9i with Oracle's Flashback Query feature.
www.yogijicreations.com
FRA ( Flashback Recovery area)
storage area (directory on disk or ASM diskgroup) that enables database Flash Backup and Recovery operations. first introduced with Oracle 10g. Related parameters:
db_recovery_file_dest db_recovery_file_dest_size db_flashback_retention_target
www.yogijicreations.com
Flashback Query ( 9i Feature)
Allows users to see a consistent view of the database as it was at a point in the past.
In Oracle 10g, we can now retrieve all versions of the rows that exist or ever existed between the time the query was issued and a point back in time.
www.yogijicreations.com
Flashback Database
Faster than traditional point-in-time recovery. Traditional recovery method: Backups and Redo logs Flashback Database is implemented using a new type of log file called the Flashback Database log. Oracle database server periodically logs before images of data blocks in the Flashback Database logs. The data block images are used to quickly back out changes to the database during Flashback Database. RVWR: similar to the LGWR (log writer) process. writes Flashback Database data to the Flashback Database logs.
www.yogijicreations.com
www.yogijicreations.com
Enabling Flashback Database
Make sure the database is in archive mode. Configure the recovery area by setting the two parameters: DB_RECOVERY_FILE_DEST DB_RECOVERY_FILE_DEST_SIZE Open the database in MOUNT EXCLUSIVE mode and turn on the flashback feature: SQL> STARTUP MOUNT EXCLUSIVE; SQL> ALTER DATABASE FLASHBACK ON; Set the Flashback Database retention target: DB_FLASHBACK_RETENTION_TARGET
www.yogijicreations.com
Flashback Drop
DROP command permanently removed objects from the database… In Oracle 10g, a DROP command places the object in the recycle bin. You can restore the object from the recycle bin at any time. Flashback table emp to before drop; drop table emp PURGE;
www.yogijicreations.com
Recycle Bin
A recycle bin contains all the dropped database objects until,
Permanently drop them with the PURGE command. Recover the dropped objects with the FLASHBACK TABLE command. There is no room in the tablespace for new rows or updates to existing rows. The tablespace needs to be extended.
www.yogijicreations.com
Flashback Table
Flashback Table allows you to recover a table or tables to a specific point in time without restoring a backup. When you use the Flashback Table feature to restore a table to a specific point in time, all associated objects, such as, indexes, constraints, and triggers will be restored. FLASHBACK TABLE emp TO SCN 76230;
www.yogijicreations.com
Flashback Transaction Query
It provides a way for you to view changes made to the database at the transaction level. It allows you to diagnose problems in your database and perform analysis and audit transactions
www.yogijicreations.com
Questions ?
For queries: [email protected]
www.yogijicreations.com
