今天客户说了一个我感觉有意思的需求:在一个库上的一张表记录所有库的ddl操作,实现方式：在一个库上建立表和触发器,其他库上通过dblink+同义词+触发器实现ddl操作记录到远程的表中.他当时写了一个触发器,但是有错误,想让我协助解决.在我们的一起努力下,解决了该触发器在dblink同义词的库上出错的问题.我这里测试使用的是10g的库做为存储所有库的ddl记录的库,11g库做为一个通过dblink插入ddl操作记录的库.
在10g数据库库中操作
1.创建记录ddl操作表

SQL> conn chf/xifenfei
Connected.
SQL> create table t_ddl_audit(
  2  db_name varchar2(30),
  3  login_user varchar2(30),
  4  ddl_time date,
  5  ip_address varchar2(20),
  6  audsid varchar2(20),
  7  schema_user varchar2(30),
  8  schema_object varchar2(40),
  9  login_tool varchar2(40),
 10  os_user varchar2(40),
 11  ddl_sql varchar2(4000));

Table created.

2.创建触发器

SQL> create or replace trigger tri_ddl_audit
  2    before ddl on database
  3  declare
  4    n           number;
  5    str_stmt    varchar2(4000);
  6    sql_text    ora_name_list_t;
  7    l_trace     number;
  8    v_module    varchar2(50);
  9    v_action    varchar2(50);
 10    str_session v$session%rowtype;
 11  begin
 12    n := ora_sql_txt(sql_text);
 13    for i in 1 .. n loop
 14      str_stmt := substr(str_stmt || sql_text(i), 1, 3000);
 15    end loop;
 16    dbms_application_info.READ_MODULE(v_module, v_action);
 17    INSERT INTO chf.t_ddl_audit
 18      (db_name,
 19       login_user,
 20       ddl_time,
 21       ip_address,
 22       audsid,
 23       schema_user,
 24       schema_object,
 25       login_tool,
 26       os_user,
 27       ddl_sql)
 28    VALUES
 29      (sys_context('USERENV', 'db_name'),
 30       ora_login_user,
 31       SYSDATE,
 32       sys_context('USERENV', 'IP_ADDRESS'),
 33       userenv('SESSIONID'),
 34       ora_dict_obj_owner,
 35       ora_dict_obj_name,
 36       v_module,
 37       sys_context('userenv', 'os_user'),
 38       str_stmt);
 39  exception
 40    when no_data_found then
 41      null;
 42  end;
 43  /

Trigger created.

3.测试触发器

SQL> conn chf/xifenfei
Connected.
SQL> create table t_xff as select * from dba_tables where rownum=1;

Table created.

SQL> select db_name,login_user,ddl_sql from t_ddl_audit;

DB_NAME                        LOGIN_USER
------------------------------ ------------------------------
DDL_SQL
-----------------------------------------------------------------
XFF                            CHF
create table t_xff as select * from dba_tables where rownum=1

在11g数据库中操作
1.创建dblink和同义词

SQL> create database link "ora10g_dblink"
  2   connect to chf
  3    identified by "xifenfei"
  4     using 'ora10g';

Database link created.

SQL> create  synonym t_ddl_audit for t_ddl_audit@ora10g_dblink;

Synonym created.

2.第一次创建触发器

SQL> create or replace trigger tri_ddl_audit
  2    before ddl on database
  3  declare
  4    n           number;
  5    str_stmt    varchar2(4000);
  6    sql_text    ora_name_list_t;
  7    l_trace     number;
  8    v_module    varchar2(50);
  9    v_action    varchar2(50);
 10    str_session v$session%rowtype;
 11  begin
 12    n := ora_sql_txt(sql_text);
 13    for i in 1 .. n loop
 14      str_stmt := substr(str_stmt || sql_text(i), 1, 3000);
 15    end loop;
 16    dbms_application_info.READ_MODULE(v_module, v_action);
 17    INSERT INTO t_ddl_audit
 18      (db_name,
 19       login_user,
 20       ddl_time,
 21       ip_address,
 22       audsid,
 23       schema_user,
 24       schema_object,
 25       login_tool,
 26       os_user,
 27       ddl_sql)
 28    VALUES
 29      (sys_context('USERENV', 'db_name'),
 30       ora_login_user,
 31       SYSDATE,
 32       sys_context('USERENV', 'IP_ADDRESS'),
 33       userenv('SESSIONID'),
 34       ora_dict_obj_owner,
 35       ora_dict_obj_name,
 36       v_module,
 37       sys_context('userenv', 'os_user'),
 38       str_stmt);
 39  exception
 40    when no_data_found then
 41      null;
 42  end;
 43  /

Trigger created.

3.测试触发器

SQL> create table t_xff as select * from dba_objects where rownum<10;
create table t_xff as select * from dba_objects where rownum<10
                                    *
ERROR at line 1:
ORA-00604: error occurred at recursive SQL level 1
ORA-02070: database  does not support  in this context
ORA-06512: at line 15

出现ORA-02070错误,估计是类此sys_context(‘userenv’, ‘os_user’)导致。

4.第二次创建触发器

SQL> create or replace trigger tri_ddl_audit
  2    before ddl on database
  3  declare
  4    n           number;
  5    str_stmt    varchar2(4000);
  6    sql_text    ora_name_list_t;
  7    l_trace     number;
  8    v_module    varchar2(50);
  9    v_action    varchar2(50);
 10    v_db_name   varchar2(50);
 11    v_ip_addr   varchar2(50);
 12    v_os        varchar2(50);
 13    v_session_id varchar2(50);
 14    str_session v$session%rowtype;
 15  begin
 16    n := ora_sql_txt(sql_text);
 17    for i in 1 .. n loop
 18      str_stmt := substr(str_stmt || sql_text(i), 1, 3000);
 19    end loop;
 20    dbms_application_info.READ_MODULE(v_module, v_action);
 21    v_db_name :=sys_context('USERENV', 'db_name');
 22    v_ip_addr :=sys_context('USERENV', 'IP_ADDRESS');
 23    v_os:=sys_context('userenv', 'os_user');
 24    v_session_id:=userenv('SESSIONID');
 25    INSERT INTO t_ddl_audit
 26      (db_name,
 27       login_user,
 28       ddl_time,
 29       ip_address,
 30       audsid,
 31       schema_user,
 32       schema_object,
 33       login_tool,
 34       os_user,
 35       ddl_sql)
 36    VALUES
 37      (v_db_name,
 38       ora_login_user,
 39       SYSDATE,
 40       v_ip_addr,
 41      v_session_id,
 42       ora_dict_obj_owner,
 43       ora_dict_obj_name,
 44       v_module,
 45       v_os,
 46       str_stmt);
 47  exception
 48    when no_data_found then
 49      null;
 50  end;
 51  /

Trigger created.

5.继续测试触发器

SQL> drop table t3;
drop table t3
*
ERROR at line 1:
ORA-00604: error occurred at recursive SQL level 1
ORA-02069: global_names parameter must be set to TRUE for this operation
ORA-06512: at line 23

根据ORA-02069,查询资料发现是通过dblink插入数据使用了变量和常量的方式混合使用导致该错误,修改触发器全部使用变量方式

6.第三次创建触发器

SQL> create or replace trigger tri_ddl_audit
  2    before ddl on database
  3  declare
  4    n           number;
  5    str_stmt    varchar2(4000);
  6    sql_text    ora_name_list_t;
  7    l_trace     number;
  8    v_module    varchar2(50);
  9    v_action    varchar2(50);
 10    v_db_name   varchar2(50);
 11    v_ip_addr   varchar2(50);
 12    v_os        varchar2(50);
 13    v_session_id varchar2(50);
 14    v_loginuser    varchar2(50);
 15     v_obj_name varchar2(50);
 16    v_owner    varchar2(50);
 17    str_session v$session%rowtype;
 18  begin
 19    n := ora_sql_txt(sql_text);
 20    for i in 1 .. n loop
 21      str_stmt := substr(str_stmt || sql_text(i), 1, 3000);
 22    end loop;
 23    dbms_application_info.READ_MODULE(v_module, v_action);
 24    v_db_name :=sys_context('USERENV', 'db_name');
 25    v_ip_addr :=sys_context('USERENV', 'IP_ADDRESS');
 26    v_os:=sys_context('userenv', 'os_user');
 27    v_session_id:=userenv('SESSIONID');
 28    v_loginuser:= ora_login_user;
 29    v_owner:=ora_dict_obj_owner;
 30    v_obj_name:=ora_dict_obj_name;
 31    INSERT INTO t_ddl_audit
 32      (db_name,
 33       login_user,
 34       ddl_time,
 35       ip_address,
 36       audsid,
 37       schema_user,
 38       schema_object,
 39       login_tool,
 40       os_user,
 41       ddl_sql)
 42    VALUES
 43      (v_db_name,
 44       v_loginuser,
 45       SYSDATE,
 46       v_ip_addr,
 47      v_session_id,
 48       v_owner,
 49       v_obj_name,
 50       v_module,
 51       v_os,
 52       str_stmt);
 53  exception
 54    when no_data_found then
 55      null;
 56  end;   
 57  /

Trigger created.

7.测试触发器

SQL> create table t_xff11 as select * from dba_tables where rownum<10;

Table created.

SQL> select db_name,login_user,ddl_sql from t_ddl_audit;

DB_NAME                        LOGIN_USER
------------------------------ ------------------------------
DDL_SQL
-----------------------------------------------------------------
ora11g                         CHF
create table t_xff11 as select * from dba_tables where rownum<10

XFF                            CHF
create table t_xff as select * from dba_tables where rownum=1

补充说明
这个方案个人感觉是一个实验室中的方案,在实际的生成环境中很难应用上
1.trigger记录ddl操作本身效率不高
2.如果某个库不能访问存储ddl操作的表的数据库,将导致该数据库所有ddl操作hang住,从而可能使得该数据库hang住的风险.