Encryption is done in I/O path – RE-ENCRYPTION SCAN/ ENCRYPTION SCAN. A background process with shared lock runs to encrypt the database. It returns immediately with success message but the database is not completely encrypted. After running the Alter SQL Server performs basic checks such as Edition Check, Read-only Filegroups, and presence of DEK etc. TDE is enabled by using ALTER DATABASE command. TDE helps with real time I/O encryption of data and log files.

Encryption should be extended to the data at rest.Data Encryption should be transparent to the applications using the database.Companies which maintain sensitive data should comply to more stringent security standards.It has the most valuable features which will help secure data by help of exploiting multiple CPUs and less increase in the disk space used to save encrypted data. This feature has been introduced to provide more security to the data stored at the database level. Transparent Data Encryption is introduced in SQL Server 2008.

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