About Oracle 11g Deduplication

By: Richard Niemiec


Deduplication can be a powerful feature that can reduce the amount of storage space needed for LOBs, as all duplicated LOBs are only stored once. If you need to reduce database disk space, SecureFiles compression and deduplication can provide significant cost savings for storage.

 

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Oracle SecureFiles utilizes memory in the form of a shared IO pool. The shared IO pool is used from the SGA and allocations are always for a specific session; therefore, the data is specific to the session. You can view the shared IO pool by querying both the V$SGAINFO and the V$SGA_DYNAMIC_COMPONENTS V$ views. If you examine the memory structures of the SGA, you can see what the shared IO pool max size is in relationship to the other database memory structures:

 

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When a session is unable to find free memory in the shared IO pool, PGA memory is used. To see PGA memory allocations, you can use the V$SECUREFILE_TIMER view, which receives an entry each time memory is allocated out of the PGA:

 

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