Please find the queries below.
1) The below one will show all the sessions.
set lines 170
set pages 10000
col event format a40
col sample_time format a40
select to_char(sample_time,'DD-MON-YY HH24:MI:SS'),SESSION_ID,SESSION_SERIAL#,SQL_ID,BLOCKING_SESSION,BLOCKING_SESSION_SERIAL#,BLOCKING_SESSION_STATUS,EVENT from dba_hist_active_sess_history where to_char(sample_time,'DD-MON-YY HH12:MI:SS') between '19-DEC-16 06:10 PM' and '19-DEC-16 06:20 PM' and BLOCKING_SESSION is not null order by 1 ;
2) The below one will show the sessions for tx enqueue row lock contention alone.
set lines 170
set pages 10000
col event format a40
col sample_time format a40
select to_char(sample_time,'DD-MON-YY HH24:MI:SS'),SESSION_ID,SESSION_SERIAL#,SQL_ID,BLOCKING_SESSION,BLOCKING_SESSION_SERIAL#,BLOCKING_SESSION_STATUS,EVENT from dba_hist_active_sess_history where to_char(sample_time,'DD-MON-YY HH12:MI:SS') between '19-DEC-16 06:20 PM' and '19-DEC-16 06:30 PM' and event like '%enq:%' and BLOCKING_SESSION is not null order by 1 ;
3) The below one will show the blocking sql text by using the sql_id
set long 10000
set pages 10000
select SQL_FULLTEXT from v$sql where SQL_ID = '&1' and rownum < 2;