Robotron's questions

我正在执行成功执行的直接路径插入。当我尝试自动跟踪执行时，我得到了ORA-12838: cannot read/modify an object after modifying it in parallel.

SQL> insert into emp_big select * from emp_big_temp;

411843 rows created.

Elapsed: 00:00:00.89

Execution Plan
----------------------------------------------------------
Plan hash value: 3203427748

-----------------------------------------------------------------------------------------
| Id  | Operation                | Name         | Rows  | Bytes | Cost (%CPU)| Time     |
-----------------------------------------------------------------------------------------
|   0 | INSERT STATEMENT         |              |   357K|    45M|  1164   (1)| 00:00:14 |
|   1 |  LOAD TABLE CONVENTIONAL | EMP_BIG      |       |       |            |          |
|   2 |   TABLE ACCESS FULL      | EMP_BIG_TEMP |   357K|    45M|  1164   (1)| 00:00:14 |
-----------------------------------------------------------------------------------------

Note
-----
   - dynamic sampling used for this statement (level=2)


Statistics
----------------------------------------------------------
         15  recursive calls
      31909  db block gets
      12829  consistent gets
          0  physical reads
   34685216  redo size
        845  bytes sent via SQL*Net to client
        802  bytes received via SQL*Net from client
          3  SQL*Net roundtrips to/from client
          1  sorts (memory)
          0  sorts (disk)
     411843  rows processed

SQL> rollback;

Rollback complete.

Elapsed: 00:00:00.18
SQL>
SQL> insert /*+ append */ into emp_big select * from emp_big_temp;

411843 rows created.

Elapsed: 00:00:00.18

Execution Plan
----------------------------------------------------------
ERROR:
ORA-12838: cannot read/modify an object after modifying it in parallel


SP2-0612: Error generating AUTOTRACE EXPLAIN report

Statistics
----------------------------------------------------------
          0  recursive calls
       4438  db block gets
       4283  consistent gets
          0  physical reads
       7648  redo size
        829  bytes sent via SQL*Net to client
        816  bytes received via SQL*Net from client
          3  SQL*Net roundtrips to/from client
          1  sorts (memory)
          0  sorts (disk)
     411843  rows processed

问题：

1. 根据 ，表emp_big的并行度设置为 1 select table_name, degree from user_tables。为什么 Oracle 强制并行插入？
2. 为什么使用autotrace trace原因ORA-12838？

Oracle做全表扫描时，为什么要扫描高水位线以下的所有行？它不知道某些行已被删除并且不应该扫描它们吗？

让我详细说明标题。

假设我们有两个表，t1并且t2. t2上面有触发器t2_trg。同一事务在 中插入/更新数据t1，然后在 中插入/更新数据t2。t2_trg被解雇并开始做它的事情。此触发器是否能够看到在 中完成的所有更改t1？

Ps 我找到了关于此问题的其他主题，但它们主要针对 SQL Server。

如何清除用户的个人资料？我找到了如何删除配置文件（也使用 CASCADE），但我想保留配置文件并将其从用户中删除。