You can discuss anything related to RMAN here.

Here is some info on RMAN channels.  You can open up quite a few channels but you need to be careful based on your OS and DB Configurations because it'll have a performance impact on your system.

RMAN Channels

The RMAN client directs database server sessions to perform all backup and recovery tasks. What constitutes a session depends on the operating system. For example, on Linux, a server session corresponds to a server process, whereas on Windows it corresponds to a thread within the database service.

The RMAN client itself does not perform backup, restore, or recovery operations. When you connect the RMAN client to a target database, RMAN allocates server sessions on the target instance and directs them to perform the operations.

An RMAN channel represents one stream of data to a device, and corresponds to one database server session. The channel reads data into PGA memory, processes it, and writes it to the output device. See "Basic Concepts of RMAN Performance Tuning" for a low-level description of how channels work.

channel

An RMAN channel represents one stream of data to or from a backup device. A channel can either be a DISK channel (used to perform disk I/O) or an SBT channel (used to perform I/O through a third-party media manager). Each allocated channel starts a new Oracle server session. The server session then performs backup, restore, and recovery operations.

Hope this helps.

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