Recovery with Archiving  «Prev  Next»

Lesson 8

ARCHIVELOG Database Recovery Conclusion

This module introduced you to various methods for performing ARCHIVELOG database recovery. You learned that the recovery method you use depends on the state of the database. You also leaned how to perform ARCHIVELOG database recovery using different methods.
Having completed this module, you should be able to:
  1. Describe the implications of instance failure with an ARCHIVELOG database
  2. Describe the different methods of recovery
  3. Describe a complete recovery operation
  4. Recover a closed database
  5. Recover an open database, initially open
  6. Recover an open database, initially closed

Recovery with Archiving Glossary

This module introduced you to the following terms:
  1. Instance failure: Instance failure means an abrupt end to an Oracle instance either due to a hardware or software problem. The system global area and background processes cease to function. Therefore, any data in the buffer that had not already been written to a datafile at the time of the instance failure will be lost. On the other hand, complete recovery recovers the damaged datafiles as well as all data that had been committed prior to the moment of instance failure.
  2. Complete recovery: Complete Oracle recovery, also known as complete media recovery, is applied to a database running in ARCHIVELOG mode. Complete recovery with archiving allows you to recover your database up to the time just prior to the occurrence of media failure.
  3. System global area: The Oracle database employs several memory structures that are contained with the System Global Area (SGA). The System Global Area contains three main in-memory structures. These memory structures may be tuned or modified by the DBA to improve performance. These memory structures include Shared Pool, Database Buffer Cache, and Redo Log Buffer.

In the next module, you learn how to perform incomplete Oracle recovery with archiving.

The following section discusses recovering an open database, initially open.

Recover Open Database

The steps involved to Recover open database in Oracle.
  1. To make sure you are pointing to the correct database ORCL, you need to set ORACLE_SID. Type 
    SET ORACLE_SID=ORCL
    you should you use at the prompt. After you finish, press Enter.
  2. To access the Server Manager in the NT environment, type SVRMGR30 at the prompt. After you finish, press Enter.
  3. Type CONNECT INTERNAL at the prompt to connect as sysdba. After you finish, press Enter.
  4. The password ORACLE is entered for you. Now you need to check whether the damaged datafile USR1ORCL.ORA is offline. Type 
    SELECT A.FILE#, A.NAME, A.STATUS, B.STATUS 
FROM V$DATAFILE A, V$DATAFILE_HEADER B 
WHERE A.FILE# = B.FILE#;

    at the prompt. After you finish, press Enter.
  5. Since the damaged datafile USRORCL.ORA is still on line, you need to take it offline before you start recovery. Enter 
    ALTER DATABASE DATAFILE C:\ORANT\DATABASE\USR1ORCL.ORA OFFLINE;

    at the prompt to to take this datafile offline. After you finish, press Enter.
  6. Now you are ready to restore the damaged datafile using the operating system command. To access the operating system, type HOST at the prompt. After you finish, press Enter.
  7. Suppose you have your backup at the path C:\ORANT\BACKUP and you original datafile path at C:\ORANT\DATABASE. Type 
    host copy
C:\ORANT\BACKUP\USR1ORCL.ORA C:\ORANT\DATABASE\USR1ORCL.ORA
    to restore the damaged datafile. After you finish, press Enter.
  8. Type EXIT to go back to the Server Manager. After you finish, press Enter.
  9. Type 
    RECOVER DATAFILE C:\ORANT\DATABASE\USR1ORCL.ORA;
    to start to recover the datafile. After you finish, press Enter.
  10. Type auto to continue the recovery automatically. After you finish, press Enter.
  11. You finished the recovery successfully. Now you need to put the datafile online. Type 
    							 
ALTER DATABASE DATAFILE
'C:\ORANT\DATABASE\USR1ORCL.ORA' ONLINE;
    at the prompt. After you finish, press Enter.
  12. You have completed the whole process of recovery. This is the end of the Simulation.


Complete Database Recovery - Quiz

Click the Quiz link below to test your knowledge about complete database recovery.
Complete Database Recovery - Quiz