Monday, December 27, 2010

Oracle Cannot Read Database Files Due to Corruption

The Oracle DBMS (Database Management System) stores data in a hierarchical format in all of its database components. Data is stored at four levels- Blocks, Extents, Tablespaces, and Segments. If any of these components is damaged, database becomes un-mountable and the database records become inconsistent. This behavior of Oracle database makes your valuable data inaccessible and causes serious data loss. In order to handle such situations, Oracle database recovery software are required.

Most commonly the Oracle database corruption starts at Tablespace level, which is the most initial level of the database. The reasons of database corruption could be anything from virus infection, improper system shutdown, application crash to operating system damage. You may encounter various error messages in such cases, while accessing the database. Such errors may be similar to the following one-

"ORA-00376: file xx cannot be read at this time"

You may encounter the above error every time you try to mount the Oracle database. A corrupt database cannot be mounted and thus it cannot be accessed. To recover Oracle database in such cases, you are required to identify the cause of this problem and then fix it using Oracle recovery solutions.


The most probable reason of this behavior of Oracle database (DBF file) is damage to the UNDO Tablespace. Corruption makes whole database unusable and inaccessible.


Go through the below DBF recovery steps to work around the corruption problem-

Modify the value of the undo_management parameter as ‘MANUAL'. By default it is set to AUTO.
Drop the damaged Tablespace and create a new UNDO Tablespace.

In majority of situations, above steps fix the problem and repair Oracle database. But in case the above
solution fails, database becomes un-mountable. In such cases, try the following solutions-

Restore database from the most recent backup. However, you are recommended to restore the database only if you have a valid and updated backup. An incomplete backup may cause further data loss.
Use third-party Oracle recovery software to repair and restore the database. They perform Oracle database recovery in virtually every database corruption situation, regardless of the cause and extent of corruption.

Such DBF recovery applications are particularly designed to recover DBF files in an extremely safe and easy way with their read-only conduct and simple user interface. They recover Oracle database along with all of its components, such as tables, reports, forms, macros, data types, and more.

Stellar Phoenix Oracle Recovery is an effective Oracle database recovery solution to repair Oracle 9i database.
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About the Author

My name is Mark Willium, I have done Ph.D in computer science and currently doing research on how to recover oracle database.

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