ORA-01180: can not create datafile 1

I was restoring a database when i got this error message
ORA-01180: can not create datafile 1

The restore did restore some file's but when it wanted to restore datafile 1
it gave the message. After some time i thought maby the file isn't on tape
anymore.

First i checked what the retention time of the backup was in rman for this database.
It was 21 days. The restore i wanted was from a backup 22 days ago.
Then in rman i ran the command : list backup of database;
It showed that the backup of 22 ago wasn't availble anymore.
It was just luck that some datafiles where still on tape but not datafile 1

The error message is at first sight a little strange.but if you know why it make's sense.
You can't create a datafile if it isn't on tape anymore.

Lesson learned: First make sure that the restore time is within your retention time.