這種應用從前景上來說非常廣,尤其是在系統切換的時候,兩個系統的表結構都有較大的變化時。但爲了實現平滑的切換,一種方案就是實現兩個異構系統
之間的雙向同步。這樣可以隨時在兩個系統之間進行切換,從而減少了切換的壓力。
雙向複製的方案很多,可以用程序實現。可以用觸發器實現。當然流複製也可以實現。
以下是我用流複製進行many-to-one複製的一種嘗試,例子很簡單,僅以此拋磚引玉!
數據庫版本:ORACLE10.2.0.1
測試環境:
源庫:stream76.com
目的庫:stream19.com
源表:
sql> desc test.t11;
Name Null? Type
----------------------------------------- -------- ----------------------------
ID NUMBER(38)
sql> desc test.t1;
Name Null? Type
----------------------------------------- -------- ----------------------------
ID NUMBER(38)
NAME VARCHAR2(30)
目的表:
SQL> desc test.t11_19
Name Null? Type
----------------------------------------- -------- ----------------------------
NO NUMBER(38)
NAME VARCHAR2(30)
sql>
sql> select * from test.t1;
ID NAME
---------- ------------------------------
444 test444
555 test555
複製規則:
t11.id+t1.name=t11_19.NO+t11_19.NAME
如何實現流複製的transformation就不寫了,請見我的前一個貼子。
http://space.itpub.net/9375/viewspace-490762
這裏僅簡單演示如何利用dml handler進行many-to-one的複製。
一 編寫dml handler並在目的庫創建此存儲過程
CREATE OR REPLACE PROCEDURE t11_dml_handler(in_any IN SYS.ANYDATA) IS
lcr SYS.LCR$_ROW_RECORD;
rc PLS_INTEGER;
object_owner VARCHAR2(30);
object_name VARCHAR2(40);
dmlcommand VARCHAR2(10);
v_name varchar2(20) := ' ';
v_old_id_anydata SYS.ANYDATA;
v_old_id number;
v_dummy PLS_INTEGER;
v_sqlcode varchar2(32);
v_sqlerrm varchar2(255);
--v_typecode PLS_INTEGER;
--v_type SYS.ANYTYPE;
non_null_anytype_for_NUMBER exception;
unknown_typename exception;
v_cnt number;
BEGIN
-- Access the LCR
rc := in_any.GETOBJECT(lcr);
object_owner := lcr.GET_OBJECT_OWNER();
object_name := lcr.GET_OBJECT_NAME();
dmlcommand := lcr.GET_COMMAND_TYPE();
if dmlcommand in ('INSERT') then
v_old_id_anydata := lcr.get_value('NEW', 'NO', 'Y');
elsif dmlcommand in ('DELETE') then
v_old_id_anydata := lcr.get_value('OLD', 'NO');
else
null;
end if;
-- Insert information about the LCR into the history_row_lcrs table
INSERT INTO strmadmin.history_row_lcrs
VALUES
(SYSDATE,
lcr.GET_SOURCE_DATABASE_NAME(),
lcr.GET_COMMAND_TYPE(),
lcr.GET_OBJECT_OWNER(),
lcr.GET_OBJECT_NAME(),
lcr.GET_TAG(),
lcr.GET_TRANSACTION_ID(),
lcr.GET_SCN(),
lcr.GET_COMMIT_SCN,
lcr.GET_VALUES('old'),
lcr.GET_VALUES('new', 'n'));
commit;
v_dummy := v_old_id_anydata.GetNUMBER(v_old_id /* OUT */);
--DBMS_OUTPUT.PUT_LINE(TO_CHAR(v_id) || ': NUMBER = ' || To_Char(v_n));
select count(*) into v_cnt fromtest.t1@stream76a where a.id = v_old_id;
if v_cnt = 1 then
select name into v_name fromtest.t1@stream76a where a.id = v_old_id;
IF object_owner = 'TEST' and object_name = 'T11_19' and dmlcommand IN ('INSERT' /*, 'DELETE', 'UPDATE'*/
) THEN
-- Add Columns
lcr.add_column('NEW', 'NAME', sys.anydata.convertvarchar2(v_name));
ELSE
lcr.add_column('OLD', 'NAME', sys.anydata.convertvarchar2(v_name));
END IF;
LCR.EXECUTE(TRUE);
elsif v_cnt = 0 then
IF object_owner = 'TEST' and object_name = 'T11_19' and dmlcommand IN ('INSERT' /*, 'DELETE', 'UPDATE'*/
) THEN
-- Add Columns
lcr.add_column('NEW', 'NAME', sys.anydata.convertvarchar2(' '));
ELSE
lcr.add_column('OLD', 'NAME', sys.anydata.convertvarchar2(' '));
END IF;
LCR.EXECUTE(TRUE);
else
null;
end if;
insert into event_log
(id, timestamp, event)
values
(seq_event.nextval,
sysdate,
'succeed! v_id=' || v_old_id || 'cnt=' || v_cnt || ',dmlcommand=' ||
dmlcommand || ',v_name=' || v_name);
commit;
exception
when others then
rollback;
v_sqlcode := sqlcode;
v_sqlerrm := sqlerrm;
insert into event_log
(id, timestamp, event)
values
(seq_event.nextval,
sysdate,
v_sqlcode || '|' || v_sqlerrm || ',v_old_id=' || v_old_id || ',cnt=' ||
v_cnt || ',v_name=' || v_name || ',dmlcommand=' || dmlcommand);
commit;
END;
/
這裏簡單起見,就寫了對insert和delete的處理過程;呵,有點懶呀!
二 在目的庫配置應用
BEGIN
DBMS_APPLY_ADM.SET_DML_HANDLER
(object_name => 'TEST.T11_19',
object_type => 'TABLE',
operation_name => 'INSERT',
error_handler => FALSE,
user_procedure => 'STRMADMIN.T11_DML_HANDLER',
apply_database_link=> NULL);
END;
/
BEGIN
DBMS_APPLY_ADM.SET_DML_HANDLER
(object_name => 'TEST.T11_19',
object_type => 'TABLE',
operation_name => 'DELETE',
error_handler => FALSE,
user_procedure => 'STRMADMIN.T11_DML_HANDLER',
apply_database_link=> NULL);
END;
/
配置好以後,可以進行如下確認:
SELECT object_name,operation_name,user_procedure,
error_handler,apply_database_link
FROM dba_apply_dml_handlers;
這樣就OK了!
測試一下:
源庫:
sql> insert into test.t11 values ('333');
1 row created.
sql> commit;
Commit complete.
目的庫:
sql> select * from test.t11_19;
NO NAME
---------- ------------------------------
333
測試刪除:
源庫:
sql> delete from test.t11;
1 row deleted.
sql> commit;
目的庫:
sql> /
no rows selected
源庫:
sql> insert into test.t11 values ('444');
1 row created.
sql> commit;
Commit complete.
目的庫:
sql> select * from test.t11_19;
NO NAME
---------- ------------------------------
444 test444
sql>
源庫:
sql> delete from test.t11;
1 row deleted.
sql> commit;
Commit complete.
sql>
目的庫:
sql> /
no rows selected