今天濤神說程序報ORA-12838錯誤,調出程序sql發現是一個大批量的insert,裏面使用了
/*+ append */的hint,於是下面做了段模擬這個錯誤實驗
session 1
SQL> create table tb_test as select * from emp where 1=2; Table created. SQL> insert /*+ append */ into tb_test select * from emp; 14 rows created. -- 注意/*+ append*/ 沒有commit SQL> select * from tb_test; select * from tb_test * ERROR at line 1: ORA-12838: cannot read/modify an object after modifying it in parallel
session 2
SQL> select * from tb_test; no rows selected
session 1 報了ORA-12838的錯誤,session正常,說明了在同一個事物中如果使用/*+ append */ insert如果沒有commit去做dml操作會這個錯誤,
進一步查詢發現表上加了類型爲6的鎖
SQL> col object_name for a20; SQL> select t2.object_name,t1.LOCKED_MODE from v$locked_object t1 join dba_objects t2 on t1.OBJECT_ID = t2.object_id; OBJECT_NAME LOCKED_MODE -------------------- ----------- TB_TEST 6
我們知道 locked mode 6: Lock table t in exclusive mode, 排他鎖限制最高的TM鎖,會禁止執行任何類型的DML語句