Error stack:
RMAN-00571: =========================================================== RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS =============== RMAN-00571: =========================================================== RMAN-03002: failure of backup plus archivelog command at 06/12/2015 12:48:21 ORA-19554: error allocating device, device type: SBT_TAPE, device name: ORA-27211: Failed to load Media Management Library Additional information: 2
This can be caused by a missing symbolic link to the media management library, in this case TSM.
Solution:
cd $ORACLE_HOME/lib ln -s /usr/tivoli/tsm/client/oracle/bin64/libobk64.a libobk.a