EMC Backup and Recovery for Oracle 11g OLTP Enabled by EMC ...

Chapter 5: Installation and Configuration
Multiplexing
RMAN
multiplexing
When using a deduplication appliance, such as a DD880, you should disable
multiplexing.
When creating backup sets, RMAN can simultaneously read multiple files from disk
and then write their blocks into the same backup set. For example, RMAN can read
from two datafiles simultaneously, and then combine the blocks from these datafiles
into a single backup piece. The combination of blocks from multiple files is called
RMAN multiplexing. Similar to NetWorker multiplexing, RMAN multiplexing has the
same negative effect on deduplication
The parameter that sets up multiplexing within Oracle is filesperset. The filesperset
parameter specifies the number of files that will be packaged together and sent on a
single channel to a tape device. This has the same effect as mixing bits from many
files, and again makes it more difficult to detect segments of data that already exist.
Therefore, to take full advantage of data deduplication, it is important to have the
filesperset parameter set to one.
EMC Backup and Recovery for Oracle 11g OLTP Enabled by EMC CLARiiON, EMC Data Domain, EMC NetWorker,
and Oracle Recovery Manager using NFS Proven Solution Guide
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