How to troubleshoot enq: TX - row lock contention?

I have the following situation.

I have RAC. On both nodes there are the locks.

On the First Node

SID EVENT                           USERNAME    BLOCKING_SESSION    ROW_WAIT_OBJ#   OBJECT_NAME LOCKWAIT            SQL_ID          STATUS
1   102 enq: TX - row lock contention   MYUSER      155                 136972          TABLE1V     0000000810EFA958    5f4bzdg49fdxq   ACTIVE
2   111 enq: TX - row lock contention   MYUSER      155                 136972          TABLE1V     0000000810EFAC98    5f4bzdg49fdxq   ACTIVE

Blocking session info

SID EVENT                       USERNAME    ROW_WAIT_OBJ#   OBJECT_NAME LOCKWAIT    SQL_ID          STATUS
1   155 SQL*Net message from client MYUSER      136971          MyTABLEIMAGES_IDPK      4hw85z8absbjc   INACTIVE

On the Second Node

SID EVENT                           USERNAME    BLOCKING_SESSION    ROW_WAIT_OBJ#   OBJECT_NAME   LOCKWAIT          SQL_ID          STATUS
1   65  enq: TX - row lock contention   MYUSER      155                 137033          FactTABLE1V   0000000810EF9B58  1mznc2z75ksdx   ACTIVE
2   111 enq: TX - row lock contention   MYUSER      155                 136972          TABLE1V       0000000810EF9818  5f4bzdg49fdxq   ACTIVE

Blocking session info

SID EVENT                       USERNAME    ROW_WAIT_OBJ#   OBJECT_NAME  SQL_ID  STATUS
1   155 SQL*Net message from client MYUSER      127176          MYTableLOG           INACTIVE

Additional Info : Blocking session SQL_TEXT

```
create or replace procedure ACTIONProcedureDELETE
(
p_ID NUMBER
)
is

cursor oldval is select r.id,r.sessionstatus
from MyTABLEIMAGES r where r.idparent=p_ID;

begin
update actionmyTableblock r set r.status='False' where ID=p_ID;

for oldvalItem in oldval loop

if oldvalItem.Sessionstatus='True' then
update MyTABLEIMAGES r set r.sessionstatus='False' where r.id=oldvalItem.Id;
else
update MyTABLEIMAGES r set r.sessionstatus='True' where r.id=oldvalItem.Id;

Query v$transaction on each node to see uncommitted sessions:

SELECT t.start_time, s.sid, s.serial#, s.username, s.status,s.schemaname, s.osuser
   , s.process, s.machine, s.terminal, s.program, s.module
   , to_char(s.logon_time,'DD/MON/YY HH24:MI:SS') logon_time
FROM v$transaction t, v$session s
WHERE s.saddr = t.ses_addr
ORDER BY start_time;

StackExchange Database Administrators Q#18569, answer score: 7