Explanation/Reference:
Explanation:
Tape I/O Slaves
RMAN allocates the tape buffers in the System Global Area (SGA) or the Program Global Area (PGA),depending on whether I/O slaves are used. If you set the initialization parameter BACKUP_TAPE_IO_SLAVES=true, then RMAN allocates tape buffers from the SGA. Tape devices can only beaccessed by one process at a time, so RMAN starts as many slaves as necessary for the number of tapedevices. If the LARGE_POOL_SIZE initialization parameter is also set, then RMAN allocates buffers from thelarge pool. If you set BACKUP_TAPE_IO_SLAVES=false, then RMAN allocates the buffers from the PGA.
If you use I/O slaves, then set the LARGE_POOL_SIZE initialization parameter to dedicate SGA memory toholding these large memory allocations. This parameter prevents RMAN I/O buffers from competing with thelibrary cache for SGA memory. If I/O slaves for tape I/O were requested but there is not enough space in theSGA for them, slaves are not used, and a message appears in the alert log.
The parameter BACKUP_TAPE_IO_SLAVES specifies whether RMAN uses slave processes rather than thenumber of slave processes. Tape devices can only be accessed by one process at a time, and RMAN uses thenumber of slaves necessary for the number of tape devices.