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Multiplexing…
Defined:
- Simultaneous read of multiple datafiles by single channel
- Write commingled blocks to backup piece
- Recommendation:
- Multiplex files likely to be restored together
Control with
- FILESPERSET parameter
- MAXOPENFILES parameter
- CONFIGURE or ALLOCATE CHANNEL commands
Notes:
Multiplexing has an effect on RMAN performance. RMAN multiplexing is the simultaneous read of multiple datafiles and the writing of commingled blocks (i.e. blocks from different datafiles) to the same backup piece (file). Since a restore will have to read the entire backup piece, it makes since to multiplex only those files likely to be restored together, if possible.
RMAN multiplexing is controlled with either the BACKUP command FILESPERSET parameter or the ALLOCATE/CONFIGURE CHANNEL command MAXOPENFILES parameter.