ORA-02055: distributed update operation failed; rollback req

ORA-02055: distributed update operation failed; rollback required

最近同事遇到一个奇怪的问题求助，以下奉上国外大神的问题重现及解决方法
 
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ORA-02055: distributed update operation failed; rollback required

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You call a remote procedure or package over a database link.
 
Now, on the other side (the remote side), there was an error encountered, but there were already some statements executed successfully.
 
Now you will need to perform a rollback before you can do a select on the calling side, or you will get this error.
 
原因：通过数据库链接调用远程存储过程或包。然而，执行过程中远程数据库有报错，，但是部分语句已成功执行
 
措施：在调用端可以查询之前，需要执行回滚操作，否则将获得以上错误提示。
 
问题重现：
 
-- First we create some test users

SQL> drop user test1 cascade;

User dropped.

SQL> drop user test2 cascade;

SQL> create user test1 identified by test1;

User created.

SQL> create user test2 identified by test2;

User created.

SQL> grant create session, create table, create trigger, create procedure, create database link to test1, test2;

Grant succeeded.

SQL> alter user test1 quota unlimited on system;

User altered.

SQL> alter user test2 quota unlimited on system;

User altered.
 
Now we connect to test 2 (remote user) and create a table

SQL> conn test2/test2@XE
Connected.

SQL> create table test2_tab(n number);

Table created.

SQL> insert into test2_tab values(1);

1 row created.

SQL> commit;

Commit complete.
 
In order to demonstrate this error, we create a trigger on the newly created table, but make sure the trigger fails. In our case, we assign a character to a number field:
 create or replace trigger test2_tab_bir
before insert on test2_tab
for each row
begin
  :new.n := 'a';
end;
/

Trigger created.
 
Connect to test1, create database link
 SQL>  conn test1/test1@XE
Connected.
SQL>

SQL> create database link test2 connect to test2 identified by test2 using 'XE';

Database link created.
 
Now we will create a procedure which will first do a successful dml, after that a dml that fails due to the incorrect trigger:
 create or replace procedure p is
begin
  -- first do a statement that executes ok
  update test2_tab@test2 set n=2;
  -- next statement will fail because of the invalid trigger
  insert into test2_tab@test2 values(1);
end;
/

Procedure created.
 
Call the procedure, it will fail:
 SQL> exec p
BEGIN p; END;

*
ERROR at line 1:
ORA-02055: distributed update operation failed; rollback required
ORA-06502: PL/SQL: numeric or value error: character to number conversion error
ORA-06512: at "TEST2.TEST2_TAB_BIR", line 2
ORA-04088: error during execution of trigger 'TEST2.TEST2_TAB_BIR'
ORA-02063: preceding 3 lines from TEST2
ORA-06512: at "TEST1.P", line 4
ORA-06512: at line 1
 
Now we have a failed distributed transaction, you need to rollback, else you will get the error when selecting ANY table/view
 SQL> select sysdate from dual;
select sysdate from dual
                    *
ERROR at line 1:
ORA-02067: transaction or savepoint rollback required

-- also happens when Oracle itself calls another select recursively (notice the ORA-00604)

SQL> select * from user_2pc_pending;
select * from user_2pc_pending
              *
ERROR at line 1:
ORA-00604: error occurred at recursive SQL level 1
ORA-02067: transaction or savepoint rollback required
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Present  By  Dylan.