1. bitmap索引

--session 1
SQL> create table t1_tx(id number,name varchar2(20)) ;

Table created.

SQL> insert into t1_tx select rownum,chr(97+mod(rownum,2)) from dual connect by level<=10;

10 rows created.

SQL> commit;

Commit complete.

SQL> select * from t1_tx;

        ID NAME
---------- ----------------------------------------
         1 b
         2 a
         3 b
         4 a
         5 b
         6 a
         7 b
         8 a
         9 b
        10 a

10 rows selected.

SQL> create bitmap index idx_bitmap_name on t1_tx(name);

Index created.

SQL> select sid from v$mystat where rownum=1;

       SID
----------
        63

SQL> update t1_tx set name='tx' where id=3;

1 row updated.

SQL> -- not commit

-- session 2:
SQL> select sid from v$mystat where rownum=1;

       SID
----------
         5

SQL> update t1_tx set name='bitmap' where id=5;
--hang
 
---session 3
SQL> select sid,
  2         chr(bitand(p1, -16777216) / 16777215) ||
  3         chr(bitand(p1, 16711680) / 65535) "Name",
  4         (bitand(p1, 65535)) "Mode",
  5         event,
  6         sql_id,
  7         FINAL_BLOCKING_SESSION
  8    from v$session
  9   where event like 'enq%';

       SID Name                   Mode EVENT                          SQL_ID                     FINAL_BLOCKING_SESSION
---------- ---------------- ---------- ------------------------------ -------------------------- ----------------------
         5 TX                        4 enq: TX - row lock contention  1qtvgrv88q2dj                              63

SQL>

2. 主外键关系，主键表插入数据不提交,外键表插入数据被阻塞

--session 1
SQL> create table parent(id number primary key);

Table created.

SQL> create table child(id number references parent,name varchar2(20));

Table created.

SQL> insert into parent values(1);

1 row created.

SQL>--not commit;

--session 2:
SQL> insert into child values(1,'a');
--hang

--session 3：
SQL> l
  1  select sid,
  2         chr(bitand(p1, -16777216) / 16777215) ||
  3         chr(bitand(p1, 16711680) / 65535) "Name",
  4         (bitand(p1, 65535)) "Mode",
  5         event,
  6         sql_id,
  7         FINAL_BLOCKING_SESSION
  8    from v$session
  9*  where event like 'enq%'
SQL> /

       SID Name                   Mode EVENT                          SQL_ID                     FINAL_BLOCKING_SESSION
---------- ---------------- ---------- ------------------------------ -------------------------- ----------------------
         5 TX                        4 enq: TX - row lock contention  d8gc19unfrcsw                              63

SQL>

3.插入主键同一值

--session 1:
SQL> create table mytab(id number primary key);

Table created.

SQL> insert into mytab values(1);

1 row created.

SQL>

--session 2:
SQL> insert into mytab values(1);
--hang

--session 3:
SQL> l
  1  select sid,
  2         chr(bitand(p1, -16777216) / 16777215) ||
  3         chr(bitand(p1, 16711680) / 65535) "Name",
  4         (bitand(p1, 65535)) "Mode",
  5         event,
  6         sql_id,
  7         FINAL_BLOCKING_SESSION
  8    from v$session
  9*  where event like 'enq%'
SQL> /

       SID Name                   Mode EVENT                          SQL_ID                     FINAL_BLOCKING_SESSION
---------- ---------------- ---------- ------------------------------ -------------------------- ----------------------
         5 TX                        4 enq: TX - row lock contention  2srnv7c1ummk0                              63

SQL>

4.ITL争用，其实这个可以明显看出来，因为在10g后，就已经有enq:TX – allocate ITL entry，但是我在这里还是把它分类在mode=4的TX锁。

注：9.2.0.8环境，因为10g以上环境，设置maxtrans无效，自动变成255
--session 1
SQL> create table test(x number) initrans 2 maxtrans 2;

Table created.

SQL> insert into test select rownum from dual connect by level<=3;

3 rows created.

SQL> commit;

Commit complete.

SQL> select * from test;

         X
----------
         1
         2
         3

SQL>
SQL> update test set x=99 where x=1;

1 row updated.

SQL>

--session 2
SQL> update test set x=99 where x=2;

1 row updated.

SQL>

--session 3:
SQL> update test set x=99 where x=3;
--hang

5.索引分裂，会伴随着enq: TX – index contention的等待。