We’re writing our snapshot controlfiles to a “non-shared” device in our RAC environment (?/dbs/snapcf_DBNAME.f) and this apparently can be a problem… but only when using RAC.
Per DocId 1473914.1, “…any instances in the cluster may write to the snapshot / backup controlfile. Hence the Snapshot controlfile need to be visible to all instances.” This hasn’t been a problem for us in the past, but apparently, since “any” instance can write to the snapshot controlfile, it finally did and threw the error.
An easy fix really, just configure RMAN to write to a shared device, in our case ASM, as seen below (see DocId 1472171.1):
RMAN> CONFIGURE SNAPSHOT CONTROLFILE NAME TO ‘+HCFLASH/DEMHT90/snapcf_DEMHT902.f’;