Wednesday, May 11, 2011

SQL Server Database Corruption on Write-Caching Enable System

Write-caching is the best way to improve data write and read process of your Microsoft SQL Server. It enhances the data reliability and makes the database transactions faster. However, in some situations, it may also lead to database inconsistency and database corruption. The problem generally occurs if Microsoft Exchange Server computer shuts down abnormally before successful completion of particular transaction. In such situations, entire database become inaccessible and you encounter severe data loss. In order to get your precious data back in such cases, you need to opt for SQL Server recovery solutions, if backup is not updated.

As a practical example of this problem, consider the following scenario with your Microsoft SQL Server that has write-caching enabled:

·         SQL Server writers a log record for 100th page in database.

·         SQL Server log record is stored in a non-battery-based cache, however database engine is informed that log writer is successful.

·         The 100th page of the database is also stored in a non-battery-based cache.

·         The Commit database transaction completes successfully without any error.

·         The SQL Server database engine recognizes the LSN (Log Sequence Number) and problem write for 100th page.

The database engine of Microsoft SQL Server continues to process as if the transactions are committed successfully on the media. At this point, if a power outage occurs, database may become inconsistent and you'll encounter severe data loss. The problem occurs because the database changes do not physically exist outside non-battery backed cache.

The crash recovery of Microsoft SQL Server database doesn't display any error in such situations because it doesn't know about lost log records. Thus it does not try to redo database transactions. Multiple scenarios of object modifications in such situations can lead to database corruption.

The database corruption is an unaccepted situation that leaves your valuable data at stake of loss. You must identify and fix this behavior using SQL database recovery solutions to get your mission-critical data back. In these critical data loss situations, an absolute backup of your precious data proves to be of great help.

If backup is not in place, MS SQL recovery tools are required to extract data from unusable data. The applications are powerful enough to methodically scan entire database and extract all your valuable data from it. SQL recovery programs are totally safe and easy to use.

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