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

本文详细介绍了在Oracle数据库11g版本中，使用/*+APPEND*/提示进行DirectPathInsert时，TM Enqueue Contention的问题及解决方法。从11.1版本开始，该提示的行为发生了改变，导致了额外的锁争用。通过文档提供的实例，解释了不同版本中提示的使用方式和影响，并总结了DirectPathLoad的两种不同提示：APPEND和APPEND_VALUES。

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

In this Document

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.

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:

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.

The behaviour of /*+ APPEND */ hint has changed in the different versions of Oracle:

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

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

The following examples clarify the behaviour explained above:

INSERT .. VALUES and APPEND HINT

Version: 10.2.0.4

--SID=159: SQL&gt; create table test_insert (id number, name varchar2(25)); SQL&gt; insert /*+ APPEND */ into test_insert values (1,'Test1'); 1 row created. select sid,type,id1,id2,lmode from v$lock where sid=159; SQL&gt; 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