RMAN backup is stuck/taking a long time

I am trying to run an RMAN backup that is either hung or is taking a very long time. Some background:

• I inherited this database, and I am unfamiliar with Oracle, as I am an SQL Server guy, so please point out / forgive any basic gaps in my knowledge
• This database is large but infrequently-used, and is loaded up with external data for analysis. There are no transactions. Therefore, the database is in NOARCHIVELOG mode.
• I need to do a one-time backup for now, so I think I don’t need a recovery catalog.
• I’m not quite sure of the database size, but it is on the order of 1TB

Here’s what I did, cobbled together from various sources on the internet:

> rman target mydatabase

shutdown;
startup mount;
run {
    allocate channel ch1 device type disk format 'C:/Backup_Folder/%U';
    backup format 'C:/Backup_Folder/db_%t_%s.bk' (database);
    release channel ch1;
}

The backup seems to be stuck on channel ch1: starting piece 1 at 01-MAY-15

RMAN creates a tiny (90K) file in C:/Backup_Folder but then nothing else has happened for over an hour. Do I just wait? Am I doing something wrong?