Oracle Recovery Manager RMAN workloads getting low compression

Summary: This article is to explain the best practices for achieving optimal deduplication (global compression) when using Oracle Recovery Manager (RMAN) for Oracle workloads. This KB article is not recommended to troubleshoot performance issues. If global compression for a MTree is not managing to surpass 1.5x - 2.0.x, ensure that RMAN is following suggested best practices for Data Domain integration. ...

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Symptoms

 Oracle workloads report low global compression in "Mtree Show Compression" output or evident in sfs_dump output.

APPLIES TO

  • All Data Domain Appliances

  • DD OS 5.4 and above

Cause

This article is to cover the best practices for achieving optimal deduplication (global compression) when using Oracle RMAN for Oracle workloads. If global compression for a MTree is not managing to surpass 1.5x - 2.0.x, check that RMAN is following suggested best practices for Data Domain integration.

This KB article is not recommended to troubleshoot performance issues.


 

Resolution

The following table features the suggested best practices for RMAN to achieve optimal deduplication performance from your Data Domain serving as a backup storage server for Oracle databases.
SETTING VALUE
 FILESPERSET  1 (unless using Oracle Optimized Deduplication)
 MAXOPENFILES  1 
Parallelism or number of channels As many as the appliance can bear; but recommend 4 to 8 channels.
 CONTROFILE AUTOBACKUP  ON
ENCRYPTION NO
COMPRESSION ALGORITHM
  • Not RMAN compression 
  • DD supports Oracle standard compression
Marker Support Default: auto
 

Oracle Optimized Deduplication

Data Domain Oracle Optimized Deduplication allows for RMAN to use multiplexing and for the DD to recognize correct block boundaries during block data changes that during multiplexing. If Oracle Optimized Deduplication is enabled, there is no requirement to set a value for parameters FILESPERSET and MAXOPENFILES. Oracle backup with different FILESPERSET now can dedupe against each other. 

Oracle Optimization Support:

  • DD Boost for Oracle RMAN 1.3 and above
  •  "DD Boost for Oracle RMAN" name is changed to "Oracle RMAN Agent" for version 4.0 and above.  

  • Deduplication improvement depends on the block size used. Best deduplication performance seen with 8k or 16k block sizes. Databases set at Oracle 2k, 4k, or 32k block sizes have shown to either not dedupe or have lower deduplication rates.

  • NetWorker client 8.2.2 and above

  • DDBEA 2.0, 2.5, 4.0

  • Virtual Synthetics (Avamar) are not supported

  • Known supported third party software: NetBackup with latest DD Boost code, Veeam, vRanger Pro TSM, and CommVault are not supported 
  • Cannot be enabled on a MTree replication destination

  • Prior to 5.5.2, app-optimization-compression is set for the file system. For DDOS after 5.5.2, app-optimization-compression can be applied per MTree.

To enable Oracle Optimized Deduplication on the Data Domain, use the following CLI command:

# mtree option set app-optimized-compression oracle1 MTree <oracle_MTree> 

NOTE:  Do not set global  optimization if there are mixed backup types on the DD. Apply the app-optimized-compression at the MTree level (oracle1) to applicable MTrees that are targets for Oracle workloads. If the block size value is not supported, turn off app-optimized-compression


# mtree option set app-optimized-compress none MTree <oracle_MTree>


Setting Oracle Optimized Deduplication at the file system level (no mixed backup types)
           # filesys option set app-optimized-compression {none|oracle1}

Additional Information

NOTE: After Oracle Optimized Deduplication is enabled, the feature will not apply to older databases. The backup is considered a new backup. Must verify that an appropriate amount of storage space is available. Expect double DD storage consumption as the worse scenario. Deduplication rate improves as old data expires.
 
If the problem with low compression for Oracle workloads still persists, contact Dell Support and seek the engagement of a Data Domain FileSystem TSE. 

Affected Products

Data Domain

Products

Data Domain, Database App Agent, DD Boost for Oracle RMAN, NetWorker, Oracle RMAN agent
Article Properties
Article Number: 000026348
Article Type: Solution
Last Modified: 15 Jul 2025
Version:  3
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