[20180823]IMU与db link.txt

[20180823]IMU与db link.txt --//当使用db link查看远程表时,实际上会产生小小的日志. --//当时如果与IMU结合在一起,可以导致IMU的失效. 1.环境: SCOTT@book> @ ver1 PORT_STRING                    VERSION        BANNER ------------------------------ -------------- -------------------------------------------------------------------------------- x86_64/Linux 2.4.xx            11.2.0.4.0     Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit Production CREATE  PUBLIC DATABASE LINK LOOPBACK CONNECT TO SCOTT IDENTIFIED BY book USING 'localhost:1521/book:DEDICATED'; create table deptx as select * from dept; 2.测试: SCOTT@book> @ &r/viewsess "IMU commits" NAME        STATISTIC#      VALUE        SID ----------- ---------- ---------- ---------- IMU commits        374          0          1 SCOTT@book> update deptx set dname=lower(dname) where deptno=10; 1 row updated. SCOTT@book> commit; Commit complete. SCOTT@book> @ &r/viewsess "IMU commits" NAME        STATISTIC#      VALUE        SID ----------- ---------- ---------- ---------- IMU commits        374          1          1 --//可以发现当前数据库IMU起作用的. SCOTT@book> @ &r/viewsess "IMU commits" NAME        STATISTIC#      VALUE        SID ----------- ---------- ---------- ---------- IMU commits        374          0          1 SCOTT@book> update deptx set dname=lower(dname) where deptno=10; 1 row updated. SCOTT@book> select sysdate from dual@loopback; SYSDATE ------------------- 2018-08-22 09:04:00 SCOTT@book> commit ; Commit complete. SCOTT@book> @ &r/viewsess "IMU commits" NAME        STATISTIC#      VALUE        SID ----------- ---------- ---------- ---------- IMU commits        374          0          1 --//当是当执行dml时有dblink的语句,IMU失效,回到原来的模式. --//viewsess.sql脚本: set verify off column name format a70 SELECT b.NAME, a.statistic#, a.VALUE,a.sid   FROM v$mystat a, v$statname b  WHERE lower(b.NAME) like lower('%&1%') AND a.statistic# = b.statistic# ;  --and a.value>0;