It is not uncommon for Oracle to have something undocumented , and this is just another case of this ailment.
We have a database in which we have two copies of the same backup, one we keep in the FRA, the other one in an external disk, which from time to time gets deleted from this second disk. But what happens after you do a crosscheck and one of those 2 backups is expired? The one in the FRA is available and the one in the external disk is expired for RMAN, but how will you see it in your listing?
Looking at the 11.2 documentation for the LIST command , it only tells you that the Status of a backup can be AVAILABLE, UNAVAILABLE, or EXPIRED, but as you can see below that is not the case with our database 🙂
When I first faced this, it got me curious as to what the meaning of the M status meant (and I still don’t know the exact meaning, but I have my supposition) . If I did a trace of my list backup summary command , I could see exactly what I knew it was happening:
This is a small result of the trace done above :
As you can see above, one copy is EXPIRED and the other one is AVAILABLE, also because each copy has a different tag name, when you list them, you have an asterisk “*” for a tag of the backupset with Key 1987.
Both of these behaviours are perfectly normal, but you won’t find them anywhere in Oracle’s Documentation, so the next time you see this in your list command, you will know the exact meaning of this status. Have you seen this before in your RMAN listings ?
P.S. For me it means Multiple or Mixed.