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

Issue: 

While running the RMAN backup command getting the following error,

cannot make a snapshot control file

released channel: c1

released channel: c2

released channel: c3

released channel: c4

RMAN-00571: ===========================================================

RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============

RMAN-00571: ===========================================================

RMAN-03009: failure of backup command on c1 channel at 02/28/2020 20:15:58

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

RMAN>  Recovery Manager complete.

(or)

RMAN backup log file shows below while running

waiting for snapshot control file enqueue

waiting for snapshot control file enqueue

waiting for snapshot control file enqueue

waiting for snapshot control file enqueue

waiting for snapshot control file enqueue

Solution:

Check any other RMAN backup process running in server level and kill the os process

$ ps -ef|grep rman

$ kill -9 pid

after killing the OS process also getting same snapshot error. Please follow the below,

Execute the following query to 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;

You should see output similar to the following (the output in this example has been truncated):

SID User Program              Module                    Action           Logon

--- ---- -------------------- ------------------------- ---------------- ---------

  785 SYS  rman@exad (TNS V1-V3) backup full datafile: ch5  0000007 STARTED  24-OCT-16

SQL> select sid,serial#,username,osuser,machine,event,program,sql_id,blocking_session,logon_time from gv$session where status like 'ACTIVE' and SID='785';

ALTER SYSTEM KILL SESSION '785,37463' IMMEDIATE;