Oracle Backup and Recovery (2 of 2)

  1. Oracle Recovery Structures and Processes.

    1. List Oracle Processes, memory, and file structures relating to recovery

      2. Online redo log group archiving is performed by either the Archive (ARCH) background process when automatic archiving is started or by a user process that issues SQL statements to archive the online redo log groups manually. The ARCH process archives a redo log group after the group becomes inactive and the log switch to the next online redo log group has completed.

      At this point the record is created in the databases control file identifying the archived redo log file. The group of online redo log files being archived cannot be reused and written to by the LGWR process until the ARCH process has concluded and released a lock on the redo log files. This ARCH locking process guarentees that the LGWR process does not accidently overwrite online redo log file that needs to be archived. When the ARCH process has completed archiving the redo log files, a second record is written to the databases control file identifying the success of the archiving process.

      The archive process uses the LOG_ARCHIVE_DEST parameter to specify the destination of the archived redo log files. This destination is usually a storage device separete from the Oracle database. The ARCH process can write out two copies of an online redo log group - the duplexing feature . The initialization parameter LOG_ARCHIVE_DUPLEX_n specifies the location of the archived redo log file. The parameter LOG_ARCHIVE_MIN_SUCCEED_DEST specifies the number of archive log destinations to which redo log group must be successfully arhcived. A missing archived redo log file renders all subsequent archived redo log files usless.

    2. Identify the importance of checkpoints,redo logs, and archives
      1. Checkpoint: A checkpoint synchronizes the write operations of the DBWR and LGRW processes.A checkpoint can occur at:
        1. A log switch
        2. The time specified in the LOG_CHECKPOINT_TIMEOUT parameter passed after the last checkpoint.
        3. The number of OS blocks specified in the LOG_CHECKPOINT_INTERVAL parameter have been written since the last checkpoint.
        4. A DBA manually uses the ALTER SYSTEM CHECKPOINT command.
        5. A tablespace is taken offline
        6. An online backup is initiated
        7. During an instance shutdown when the NORMAL IMMEDIATE, or TRANSACTIONAL option is specified.
      2. (On-line)Redo Logs:Record all changes made to the database and are used to recover the database at a desired point in time. Redo Logs are stored in groups (named redo log groups ), these groups are composed of copies of the same file, however the creation of groups ensures high-availablity and throughput for the database, at least two redo log groups should exist with each group having the same size and the same number of members(copies).
      3. Archives: Are created each time an redo log group becomes inactive and the log switch to the next redo log group has completed. As mentioned previously these archived logs allow full recoverability without the need to go back to tape, Oracle can access these archived log files and update the database. The creation of these archived log files is recorded in the database control file.
    3. Multiplex controlfiles and redo log files.

      4. To multiplex the controlfiles:

      1. Once the database is shutdown, it is necessary to copy the control files via the OS to the desired (mirrored) locations.
      2. Modify the init.ora parameter CONTROL_FILES and indicate where the new mirrored (multiplexed) control-file can can be accessed.

      To Multiplex redo log files :

      The multiplexing is specified while the database is in mount and is done through the alter database command , the following creates a new log group.

       alter database 
>add logfile group 5 
> ('/u02/app/oradata/OSMOSIS/log_1c.dbf',
>  /u05/app/oradata/OSMOSIS/log_2c.dbf') size 5M;

      To add a new log file to an existing group: 

       alter database
>add logfile member '/u05/app/oradata/OSMOSIS/log_3c.dbf'
>to group 3;

      When adding a file to a redo log group there is no need to specify the size, because the group has already been indicated , besides all the redo log files in the group must be of the same size.

    4. List the types of failures.

      5. The following are types of failures:

        1. User Process Failure : When an Oracle user process ends abnormally, the PMON process takes care of this failure.
        2. Instance Failure : When the Oracle instance fails. The SMON process performs instance recovery at startup using the online redo log files.
        3. Media Failure : When files needed by the database are no longer accessible due to a hard disk crash, controller failures,etc.
    5. Describe the structures for instance and media recovery
    6. Describe the deferred transaction recovery concept

  2. Oracle Backup and Recovery Configuration

    1. Identify recovery implications of operating in NOARCHIVE mode.
    2. Describe the differences between ARCHIVELOG and NOARCHIVELOG modes.
    3. Configure the database for ARCHIVELOG and automatic archiving
    4. Use init.ora to configure multiple destinations for archived log files and multiple archive processes.
    5. Perform manual archive of logs.

  3. Physical Backup without Oracle Recovery Manager

    1. Describe the recovery implications of closed and opened database backups.
    2. Perform closed and opened database backups.
    3. Identify the backup implications of the logging and nologging options
    4. Identify the different types of control file backups
    5. Discuss backup issues associated with the read-only tablespaces.
    6. List the data dictonary views useful for backup operations.

  4. Complete Recovery without Recovery Manager

    1. In NOARCHIVELOG and ARCHIVELOG mode: Note the implications of a media failure.
    2. In NOARCHIVELOG and ARCHIVELOG mode: Recover a database in different situations.
    3. In NOARCHIVELOG and ARCHIVELOG mode: Restore files to a different location if media failure occurs
    4. List the dictionary views required to recover database after a media failure

  5. Incomplete Recovery with Archiving

    1. Determine when to use an incomplete recovery to recover the system
    2. Perform an incomplete database recovery
    3. Recover after losing current and inactive nonarchive redo log files

  6. Oracle Export and Import Utilities

    1. Use the Export utility to create a complete logical backup of a database object
    2. Use the Export utility to create an incremental backup of a database object
    3. Invoke direct-path method export
    4. Use the import utility to recover a database object.
    5. Perform a Tablespace point-in-time-recovery (TSPITR) with or without the transporatable tablespace feature.

  7. Additional Recovery Issues

    1. List the methods for minimizing downtime:perform parallel recovery, start recovering a database with missing data files, re-create lost temporary or index tablespaces.
    2. Reconstruct lost or damaged controlfiles.
    3. List recovery issues associated with read-only tablespaces.

  8. Oracle Utilities Troublshooting

    1. Use log and trace files to diagnose backup and recovery problems
    2. Detect corruptions by using different methods
    3. Detect and mark corrupted blocks by using DBMS_REPAIR package
    4. Use DBVERIFY utility
    5. Use the LogMiner utility to analyze redo log files to recover by undoing changes.

  9. Oracle Recovery Manager

    1. List the capabilties of Oracle Recovery Manager (RMAN)
    2. Describe the components of RMAN
    3. Connect to RMAN without a recovery catalog
    4. Start up and shutdown a target database using RMAN

  10. Oracle Recovery Manager

    1. List the capabilties of Oracle Recovery Manager (RMAN)
    2. Describe the components of RMAN
    3. Connect to RMAN without a recovery catalog
    4. Start up and shutdown a target database using RMAN

  11. Oracle Recovery Catalog Creation and Maintanence

    1. Describe the considerations for using a recovery catalog
    2. Describe the components of a recovery catalog
    3. Create a recovery catalog
    4. Maintain the recovery catalog using RMAN commands
    5. Query the recovery catalog to generate reports and lists
    6. Create,store,and run scripts.

  12. Backups using RMAN

    1. Describe backup concepts using RMAN
    2. Describe types of RMAN backups
    3. Perform incremental and cumulative backups
    4. Tune backup operations
    5. View information from the data dictonary

  13. Restoration and Recovery using RMAN

    1. Restore and Recovery considerations using RMAN
    2. Restore a Database in NOARCHIVELOG mode
    3. Restore and recover a Tablespace
    4. Restore and recover a Datafile
    5. Incomplete recover using RMAN

  14. Oracle Standby Database

    1. Explain the use of a standby database
    2. Configure initialization parameters
    3. Create,maintain and activate a Standby database
    4. Describe Managed Recovery Mode
    5. Set a standby database in read-only mode
    6. Describe the process of propagating structural changes to a standby database
    7. Describe the impact of nologging actions on the primary database