In RMAN channels can either be allocated implicitly or explicitly
To allocate channels explicitly use the ALLOCATE CHANNEL and RELEASE CHANNEL statements within a RUN block
For Standard Edition databases only one channel can be allocated. Backup and restore operations will be processed serially.
For Enterprise Edition databases one or more channels can be allocated. If multiple channels are allocated then backup and restore operations may be processes in parallel.
Channels are allocated using the ALLOCATE CHANNEL statement
ALLOCATE CHANNEL ch11 TYPE DISK; ALLOCATE CHANNEL ch12 TYPE DISK;
The ALLOCATE CHANNEL statement takes a number of options.
To specify a maximum piece size use MAXPIECESIZE. For example to restrict each backup piece to 5G use:
ALLOCATE CHANNEL ch11 TYPE DISK MAXPIECESIZE 5G;
Channels are released using the RELEASE CHANNEL statement.
RELEASE CHANNEL ch11; RELEASE CHANNEL ch12;