ORA-00230: operation disallowed: snapshot control file enqueue unavailable

If one RMAN job is already backing up the control file while another needs to create a new snapshot control file, then we may see the following message:

ORA-00230: operation disallowed: snapshot control file enqueue unavailable

Below query will determine which job is causing the wait:

SELECT s.sid, username AS "User", program, module, action, logon_time "Logon", l.*
FROM v$session s, v$enqueue_lock l
WHERE l.sid = s.sid and l.type = 'CF' AND l.id1 = 0 and l.id2 = 2;