I got following enviroments:

The customer already has a Legato backup (written to tape),now I need to make rman backup write to disk(not to replace tape,just as extra backup way),and transfer disk backups to remote place.

for avoiding control file inconsistent,I need to backup once,produce two backup data (one into tape and another into disk)at same time.

Can I use :

allocate channel d1 type disk;
allocate channel t1 type sbt_tape;

to produce two backup data at same time.