Posts Tagged database recovery

ShwetaHow to overcome DBF Corruption-

Monday, April 26th, 2010

Database computing- major presence of Oracle, Oracle is an RDBMS (Relational Database Management System), developed and marketed by Oracle Corporation. It stores all your valuable data in the DBF file. The DBF file contains all Oracle database objects, such as tables, reports, forms, macros, views, constraints, triggers, stored procedures, and more.

If any of these database objects or the entire database gets damaged, you can not access your valuable data from it. In such circumstances, Oracle Database Recovery software is required to extract data from the database.

In order to overcome DBF corruption, Oracle offers a number of methods to detect and repair data files. These options include:

DBVerify- It is an external command-line utility, which enables you to validate offline data files of Oracle database. In addition to the offline data files, you can also use this utility for checking validity of the backup data files.

ANALYZE … VALIDATE STRUCTURE- It is used to verify every single data block in the analyzed object. If this tool finds any corruption, rows are added to INVALID_ROWS table.

DB_BLOCK_CHECKING- If DB_BLOCK_CHECKING argument is set as TRUE, Oracle carries out a walk-through of the data in database block for checking whether it’s self-consistent or not. This block checking process may add 1 to 10% overhead to server. This setting is recommended only if you can accept the overhead.

DBMS_REPAIR- It enables you to find and fix database corruption. This process needs two administration Oracle database tables for holding the list of damaged blocks and the index keys which point to those damaged blocks.

Source: programmersheaven.com

http://www.all1tunes.com

http://www.all1martpro.com

Tags: , , , , ,
Posted in Opensource, Purely Technical | No Comments »

NaggieDBCC CHECKDB unable to resolve SQL Database corruption

Thursday, April 22nd, 2010

The logical and physical integrity of all SQL Server database tables is performed by DBCC CHECKDB command. The command performs and divides its operations in three different phases.

The first phase checks the consistency of the allocation structures in disk space, the second phase checks the integrity of all pages and their structures, and the last phase checks the catalog consistency.

If critical errors are found in any of the phases, the DBCC CHECKDB command terminates immediately. This happens when the SQL Server database is badly corrupted, and is beyond the repairing capabilities of DBCC CHECKDB command. In such cases, if you need to access the database records, then you will need to restore the database records from a valid backup. But, if no backup is available or backup falls short to restore the required amount of data, then you will need to repair the database by using advanced MS SQL Server Recovery application.

Let’s consider a practical scenario, where you receive the below error message when you attempt to access one of your table records-

Table error: Object ID O_ID1, index ID I_ID1 cross-object chain linkage. Page P_ID1 points to P_ID2 in object IDO_ID2, index ID I_ID2.

The above error message primarily results in inaccessibility of all the table records. Additionally, the error message pops up every time you attempt to access the table records.

Cause: Reason of error

The above table error message occurs when the next page pointer of P_ID1 page points to different object. This can happen either due to logical corruption factors or physical crash of a system component.

Resolution: Steps to be used to resolve the above error message

Database table corruption, if caused due to physical damage, can be resolved by changing the damaged system component. For logical table corruption reasons, run DBCC CHECKDB command with appropriate repair clause.

While the physical corruption issues can be resolved easily changing the system component, the probability of logical corruption problems being resolved by DBCC CHECKDB command is slightly less. In such cases, you will need to use advanced Recovery application to repair the database table. A SQL Repair software can be easily downloaded from Internet.

Source: www.programmersheaven.com

http://get-a-designer.com

http://www.all1sourcetech.com

Tags: , , , , , ,
Posted in Purely Technical | No Comments »

ShwetaHow to Avert and Resolve Oracle Database Corruption

Friday, April 16th, 2010

A database administrator needs to perform various operations like performing incremental backups, identifying and resolving network issues, viewing archive log destination, error generation in alert log, etc. in order to ensure that the database always remains in a running state. However, the possibility of database corruption exists due to human mistakes, virus attacks, and hardware corruption.

Database remains unmountable in most cases after it is corrupted, further rendering to inaccessibility of all its records. In such situations, if the administrator wants to access the Oracle database records, then he/she will need to use a cold backup to restore the database. However, if the administrator has not created any backup or the backup is not sufficient to meet all his/her requirements, then he/she needs to use an advanced third-party Oracle Recovery utility to repair the database.

Let’s consider a practical case, where you, as a database administrator, perform below steps:

1.You copy your database file when your database is alive.
2. Then you update the table stored in the data file.
3. After this, you shutdown the database using ’shutdown immediate’ command and change the datafile with its ‘alive’ copy.

After this, when you try to mount your Oracle database, it does not mount. The reason is-

The fundamental reason for unmountability of the database is corruption in datafile. To prevent the corruption of datafile, you should never follow the above steps sequentially.

Resolution:

It is advisable to restore the database from a standby database in order to resolve datafile corruption and to mount your Oracle database. However, if no such database exists, then you will need to repair the database. To effectively do so, you will need to search for a commercial dbf recovery application that can repair your corrupted database.

A repair tool to recover Oracle database and to bring it back to a reusable state can be easily downloaded from the Internet. Such tools can Recover Oracle Database after any logical corruption scenario using powerful recovery algorithms. Moreover, these tools do not make any change in the original database, making them completely non-destructive in nature.

For most of the Oracle database administrators, Oracle Recovery Software is a utility that they use to recover Oracle database after all kinds of logical crashes. The tool supports recovery of Oracle 9i databases. Designed for Windows XP and 2003, the read only software leaves the original database untouched and unmodified.

Tags: , , , , , ,
Posted in Editorial, Purely Technical | No Comments »