All of us using backup techniques maybe it will be different but the aim is one , saving your data
some error could be appear while you doing backup but everything can be solved one of this errors
but what is this mean ?
deadlock : situation where in two or more competing actions are each waiting for the other to finish
so when you have two backup not necessary backup btw it could be session , backup-1 will wait backup-2 and vice verse ...
In rman backup its Bug 6830296 accroding to meta-link ID 779095.1
Solution is :
In Rman catalog database create the following indexes :-
CREATE INDEX tfatt_i_sck on tfatt(start_ckp_key)
CREATE INDEX tfatt_i_eck on tfatt(end_ckp_key)
Check for availability of one off patch using the following link Patch 6830296