ORA-48132: requested file lock is busy, [HM_RUN]

Alert log reports the below error in alert.log 

Errors in file D:\ORACLE\APP\ORACLE\diag\rdbms\***\***\trace\*****_ora_18656.trc:

ORA-48132: requested file lock is busy, [HM_RUN] [D:\ORACLE\APP\ORACLE\diag\rdbms\***\***\lck\AM_1618_3044626670.lck]

It's during the RMAN backups are running.

When the RMAN backup is run querying the below output shows RMAN is Waiting on "ADR file lock" wait event

Select inst_id, sid, CLIENT_INFO ch, seq#, event, state, seconds_in_wait secs from gv$session where program like '%RMAN%' and wait_time = 0 and not action is null;

RMAN is acquiring ADR lock and this Lock is not released by OS and hence the error in the Alert log. 

To Fix 

To prevent the error message from getting reported in Alert log you can include the below event in the Rman backups script

Rman>

run {sql "alter system set events ''logon trace name krb_options level 20''";

sql "alter session set max_dump_file_size=''5K''";

allocate channel t1 <sbt or disk channel> ;

allocate channel t2 <sbt or disk channel> ;

sql "alter system set events ''logon trace name krb_options off''";

release channel t1;

release channel t2;

}