RMAN uses
two different types of buffers for I/O: disk and tape. RMAN multiplexing
determines how RMAN allocates disk buffers. RMAN multiplexing is the
number of files in a backup read simultaneously and then written to the same
backup piece. The degree of multiplexing depends on the FILESPERSET parameter
of the BACKUP command as well as the MAXOPENFILES parameter of the CONFIGURE
CHANNEL or ALLOCATE CHANNEL command.
For
example, assume that you back up two data files with one channel. You set
FILESPERSET to 3 and MAXOPENFILES to 8. In this case, the number of files in
each backup set is 2 (the lesser of FILESPERSET and the files read by each
channel) and the level of multiplexing is 2 (the lesser of MAXOPENFILES and the
number of files in each backup set).