Explanation: stands for Serial Backup Tape. Configuring Parallel Channels for Disk and SBT Devices The number of channels available for a device type when you run a command determines whether RMAN reads or writes in parallel. As a rule, the number of channels used in executing a command should match the number of devices accessed. For tape backups, allocate one channel for each tape drive. References: Oracle Database, Backup and Recovery User's Guide, 12 Release 2 (January 2017), page 5-6