4.第二个测试

    D:\>sqlplus "/ as sysdba"

    SQL*Plus: Release 9.2.0.6.0 - Production on Mon Jan 17 11:48:50 2005

    Copyright (c) 1982, 2002, Oracle Corporation. All rights reserved.

    Connected to an idle instance.

    11:48:50 SQL> startup

    ORACLE instance started.

    Total System Global Area 101785428 bytes

    Fixed Size 454484 bytes

    Variable Size 75497472 bytes

    Database Buffers 25165824 bytes

    Redo Buffers 667648 bytes

    Database mounted.

    Database opened.

    11:49:03 SQL> create table test (name varchar2(20));

    Table created.

    Elapsed: 00:00:00.04

    11:49:32 SQL> insert into test values('aaaaaaaaaaaaaaaaaaaa');

    1 row created.

    Elapsed: 00:00:00.00

    11:49:32 SQL> insert into test values('bbbbbbbbbbbbbbbbbbbb');

    1 row created.

    Elapsed: 00:00:00.00

    11:49:32 SQL> insert into test values('cccccccccccccccccccc');

    1 row created.

    Elapsed: 00:00:00.00

    11:49:32 SQL> commit;

    Commit complete.

    Elapsed: 00:00:00.00

    11:49:34 SQL>

    --注意这里是提交时间

    11:49:34 SQL>

    11:49:35 SQL>

    --等待时间流逝一秒

    11:49:36 SQL>

    11:49:37 SQL> drop table test;

    Table dropped.

    Elapsed: 00:00:00.06

    11:49:44 SQL> shutdown immediate;

    Database closed.

    Database dismounted.

    ORACLE instance shut down.

    11:49:54 SQL> exit

    Disconnected from Oracle9i Enterprise Edition Release 9.2.0.6.0 - Production

    With the Partitioning, OLAP and Oracle Data Mining options

    JServer Release 9.2.0.6.0 - Production

    D:\>sqlplus "/ as sysdba"

    SQL*Plus: Release 9.2.0.6.0 - Production on Mon Jan 17 11:50:42 2005

    Copyright (c) 1982, 2002, Oracle Corporation. All rights reserved.

    Connected to an idle instance.

    11:50:42 SQL> startup mount;

    ORACLE instance started.

    Total System Global Area 101785428 bytes

    Fixed Size 454484 bytes

    Variable Size 75497472 bytes

    Database Buffers 25165824 bytes

    Redo Buffers 667648 bytes

    Database mounted.

    11:50:59 SQL> alter session set nls_date_format='yyyy-mm-dd hh24:mi:ss';

    Session altered.

    Elapsed: 00:00:00.00

    11:51:20 SQL> recover database until time '2005-01-17 11:49:35';

    Media recovery complete.

    --此时恢复到提交一秒之后

    11:51:22 SQL> alter database open resetlogs;

    Database altered.

    Elapsed: 00:00:03.09

    11:51:32 SQL> select * from test;

    NAME

    --------------------

    aaaaaaaaaaaaaaaaaaaa

    bbbbbbbbbbbbbbbbbbbb

    cccccccccccccccccccc

    Elapsed: 00:00:00.00

    --数据得以恢复

    结论:

    Oracle能够恢复的时间精度为1秒，但是在Oracle数据库内部，用以产生SCN的时间点有更为精确的精度。

    所以，如果你指定秒级恢复，如11:57:28，那么秒后的精度被置00，反而就落在了提交之前。（猜测）

    而等待下一秒来到时，这种情况就不会出现了。