This post is related to 12c and an active database duplication for a standby I did in my lab environment. I’d say although I first encountered it on 12c there is a chance you run into a similar situation with earlier releases too.
I would normally use ASM for all my databases to make my life easier but this time I had to be mindful of the available memory on the laptop-which at 8 GB-is not plenty. So I went with file system setup instead. After the initial preparations I was ready to launch the one-liner on the standby database:
RMAN> duplicate target database for standby from active database;
This worked away happily for a few moments only to come to an abrupt halt with the below error message. I have started the duplication process on the standby.