Oracle Insert TX-Lock 발생

Oracle Insert TX-Lock 발생 

링크  - https://uhesse.com/2017/11/27/why-insert-causes-tx-row-lock-contention-or-tm-contention-in-oracle/

## SESSION 1
TEST> create table check_lock ( a1 number, a2 varchar2(100)); 
Table created.
TEST> create unique index xuk_check_lock on check_lock ( a2 ); 
Index created.
TEST> insert into check_lock values ( 1, 'a');
1 row created.
TEST>  
## SESSION 2
TEST> insert into check_lock values ( 1, 'a');
## MONITORING SESSION
TEST> select 
  2     (select username from v$session where sid=a.sid) blocker,
  3     a.sid,
  4     ' is blocking ',
  5     (select username from v$session where sid=b.sid) blockee,
  6     b.sid
  7  from 
  8     v$lock a, 
  9     v$lock b
 10  where 
 11     a.block = 1
 12  and 
 13     b.request > 0
 14  and 
 15     a.id1 = b.id1
 16  and 
 17     a.id2 = b.id2;
BLOCKER                               SID 'ISBLOCKING'  BLOCKEE                               SID
------------------------------ ---------- ------------- ------------------------------ ----------
SYS                                    42  is blocking  SYS                                    34
TEST>