Simple RMAN question

Okay, I know there must be a way to do this but none of us here are very experienced at RMAN and I haven't found it in my documentation searches.

We want to do a level 0 backup once a week and incremental backups daily on one of our databases. We backup to disk and then copy the backups to tape.

In order to conserve space we'd like to delete the level 0 backup but when we do that the validation of the incremental backup fails. Is there any way around this?

Thanks,
Jay Miller

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