Direct Path Insert与 enq:TM

Direct Path Insert - APPEND HINT and TM Enqueue LOCK Behaviour (文档 ID 1317447.1)

文档 1317447.1

In this Document

Symptoms

Changes

Cause

Solution

References

Applies to:

Oracle Database - Enterprise Edition - Version 9.2.0.1 to 11.1.0.8 [Release 9.2 to 11.1]

Oracle Database - Personal Edition - Version 9.2.0.1 to 11.1.0.8 [Release 9.2 to 11.1]

Oracle Database - Standard Edition - Version 9.2.0.1 to 11.1.0.8 [Release 9.2 to 11.1]

Information in this document applies to any platform.

Issue is seen in 11.1 not on other Versions

Symptoms

In 11.1 , using the /*+ APPEND */ hint to do direct path insert , TM Enqueue Contention occurs.

在Oracle11.1，使用APPEND 提示进行 direct path insert，会发生TM锁争用。

Changes

After having upgraded to 11.1.0.7

Cause

Change in the behaviour of the APPEND hint (Direct Path Insert)

Solution

It is explained in documentation that direct-path insert obtains exclusive locks on the table:
根据文档解释，direct-path insert会在表上产生独占锁

During direct-path INSERT, the database obtains exclusive locks on the table (or on all partitions of a partitioned table). As a result, users cannot perform any concurrent insert, update,
or delete operations on the table, and concurrent index creation and build operations are not permitted. Concurrent queries, however, are supported, but the query will return only the information before the insert operation.
在做 direct-path INSERT这一过程中，数据库对表产生独占锁，如果是分区表多整个分区产生独占锁

The behaviour of /*+ APPEND */ hint has changed in the different versions of Oracle:
根据Oracle版本不同， /*+ APPEND */的行为也会发生改变。

In Oracle 10g and previous releases the APPEND hint is ignored when specifying INSERT..VALUES. Thus even though stated, the insert will be done in conventional mode and not use direct-path insert into the buffer cache. When using INSERT..SELECT the hint
will be honoured

在Oracle10G 及以前的版本，在INSERT VALUES 语句中，APPEND提示会被忽略掉。也就是说INSERT语句会按照传统模式，并不会使用 direct-path，当使用INSERT..SELECT 时提示生效。

On 11g Release 1, the APPEND hint will be honoured for an INSERT with VALUES and the row will be inserted directly into datafiles, bypassing the buffer cache.

在Oracle 11.1中，APPEND提示在INSERT VALUES 语句中仍然生效，行会直接插入到数据文件中，绕过buffer cache。

In 11g release 2, a new hint has been added, /*+ APPEND_VALUES */ that will load the data directly into the datafiles.

在11.2中，一个新的提示 /*+ APPEND_VALUES */ 会使数据直接装载到数据文件中
To summarize, there are now 2 different hints for direct-path load:

APPEND: Instructs Oracle to use direct-path INSERT with the subquery syntax of the INSERT statement.

提示ORACLE 在带有子查询的语句使用direct-path INSERT

APPEND_VALUES: Instructs Oracle to use direct-path INSERT with the VALUES clause.

提示ORACLE在INSERT VALUES语句中使用 direct-path INSERT
The following examples clarify the behaviour explained above:
INSERT .. VALUES and APPEND HINT


Version: 10.2.0.4

--SID=159: SQL> create table test_insert (id number, name varchar2(25)); SQL> insert /*+ APPEND */ into test_insert values (1,'Test1'); 1 row created. select sid,type,id1,id2,lmode from v$lock where sid=159; SQL> SID TY ID1 ID2 LMODE ---------- -- ---------- ---------- ---------- 159 TM 61245 0 3 159 TX 262153 3571 6

APPEND hint ignored and lock mode=3 Row Exclusive

Version: 11.1.0.7

--SID=131:
SQL> create table test_insert (id number, name varchar2(25));
SQL> insert /*+ APPEND */ into  test_insert  values (1,'Test1');

1 row created.

select sid,type,id1,id2,lmode from v$lock where sid=131;

SQL>
SID TY        ID1        ID2      LMODE
---------- -- ---------- ---------- ----------
131 TM      84239          0          6
131 TX      65548       4981          6

APPEND hint honoured and lock mode=6 Exclusive

Version: 11.2.0.3

--SID=59
SQL> create table test_insert (id number, name varchar2(25));
SQL> insert /*+ APPEND */ into  test_insert  values (1,'Test1');

1 row created.

select sid,type,id1,id2,lmode from v$lock where sid=59;

SID TY        ID1        ID2      LMODE
---------- -- ---------- ---------- ----------
69 TM      96843          0          3
69 TX     196640       3301          6

APPEND hint ignored and lock mode=3 Row Exclusive

INSERT .. VALUES and APPEND_VALUES HINT

Version: 11.2.0.3

--SID=134
SQL> create table test_insert (id number, name varchar2(25));
SQL> insert /*+ APPEND_VALUES */ into  test_insert  values (1,'Test1');

1 row created.

SQL> select sid,type,id1,id2,lmode from v$lock where sid=134;

SID TY        ID1        ID2      LMODE
---------- -- ---------- ---------- ----------
134 TM      96843          0          6
134 TX      65565       7849          6

New APPEND_VALUES hint honoured and lock mode=6 Exclusive

INSERT .. SELECT and APPEND HINT



All Versions

--SID=77
SQL> insert  /*+ APPEND */ into  test_insert select object_id,object_name from user_objects;

59 rows created.

SQL> select sid,type,id1,id2,lmode from v$lock where sid=77;

SID TY        ID1        ID2      LMODE
---------- -- ---------- ---------- ----------
77 TM      96843          0          6
77 TX     589827       8029          6

APPEND hint honoured and lock mode=6 Exclusive

References

NOTE:1019527.6 -
Script to Check for Foreign Key Locking Issues for a Specific User

NOTE:842374.1 -
APPEND Hint (Direct-Path) Insert with Values Causes Excessive Space Usage on 11G