Best Practices for Oracle Databases That Use Transparent Data Encryption (TDE) or Tablespace Encryption (TSE)
Article ID: 84522
Article Type: Best Practices
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If you have an Oracle database that uses Transparent Data Encryption (TDE) or Tablespace Encryption (TSE), the encrypted data may or may not yield deduplication or compression savings due to the nature of the data.
Consider using the following parameters to determine the best compression and deduplication savings:
RMAN compression
The BFS value
The Commvault compression option
Check Exadata and Hybrid Columnar Compression (HCC) used in your database. For more information about HCC you can download the Oracle Hybrid Columnar Compression PDF from the Oracle documentation.
Use the following settings to achieve the best backup space-saving rates when you have an Oracle database that uses TDE or TSE:
Enable Commvault compression.
Enable Commvault deduplication. For an example of configuring deduplication, see Configuring Disk Storage.
Disable the use of Oracle RMAN compression. The following commands configure the enabling or disabling of RMAN compression:
CONFIGURE DEVICE TYPE 'SBT_TAPE' BACKUP TYPE TO COMPRESSED BACKUPSET; – enables backups to be compressed by RMAN
CONFIGURE DEVICE TYPE 'SBT_TAPE' BACKUP TYPE TO BACKUPSET; – disables backups being compressed by RMAN. Use this command to disable RMAN compression.
Set the data files BFS value to 1 for the Oracle subclient properties. This setting ensures that RMAN does not randomly combine the contents of multiple data files into a single buffer. This could result in producing a new block for the same old data. For information about configuring the BFS value, see Setting the Oracle Subclient RMAN Performance Tuning Parameters.
The Commvault compression algorithm results in space savings but may not meet expectations. By default, Commvault uses LZO compression. You can configure the use of GZIP compression in the Commvault settings to see if better savings can be achieved with GZIP compression. Use the nCOMPRESSIONSCHEME setting to determine if the use of GZIP results in better compression. For information about configuring the setting, see CommCell Settings. For information about the setting values, see nCOMPRESSIONSCHEME Setting. Note that GZIP compression is more CPU intensive than LZO compression.
If HCC is enabled, RMAN backups will not result in any deduplication savings since RMAN processes decompressed bytes and this never yields any deduplication savings. In this case, it is best to use RMAN compression to reduce the data size and not to use Commvault compression and deduplication.
Even if HCC is not enabled but Commvault deduplication is not possible because the whole dataset is changing between two full backups and Commvault compression does not result in adequate savings, RMAN compression alone may result in some savings.
If the database is on Exadata and uses HCC, using TDE or TSE and HCC will not yield any deduplication savings. In this case, use only RMAN compression to reduce the backup size.
To test deduplication rates after changing these parameters, run two consecutive full backups. The second full backup will result in the new deduplication rates.
