當用戶密碼即將過期時，在登錄時Oracle會提示ORA-28002錯誤，但是并不會影響正常的登錄。
本來認為這個信息并沒有太大的影響，但是沒想到這個tb錯誤會導致SET AUTOTRACE功能失效：
solaris*orcl-/home/oracle$ sqlplus test/test
SQL*Plus: Release 11.2.0.3.0 Production on Fri Jul 13 11:27:28 2012
Copyright (c) 1982, 2011, Oracle. All rights reserved.
ERROR:
ORA-28002: the password will expire within 1 days
Connected to:
Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - 64bit Production
With the Partitioning, Oracle Label Security and Real Application Testing options
SQL> set autot on
ERROR:
ORA-28002: the password will expire within 1 days
SP2-0619: Error while connecting
SP2-0611: Error enabling STATISTICS report
SQL> alter user test identified by test;
User altered.
SQL> set autot on
ERROR:
ORA-24315: illegal attribute type
SP2-0619: Error while connecting
SP2-0611: Error enabling STATISTICS report
SQL> exit
Disconnected from Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - 64bit Production
With the Partitioning, Oracle Label Security and Real Application Testing options
solaris*orcl-/home/oracle$ sqlplus test/test
SQL*Plus: Release 11.2.0.3.0 Production on Fri Jul 13 11:27:52 2012
Copyright (c) 1982, 2011, Oracle. All rights reserved.
Connected to:
Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - 64bit Production
With the Partitioning, Oracle Label Security and Real Application Testing options
SQL> set autot on
SQL> insert into t values (1, 'a');
1 row created.
Execution Plan
----------------------------------------------------------
---------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
---------------------------------------------------------------------------------
| 0 | INSERT STATEMENT | | 1 | 12 | 1 (0)| 00:00:01 |
| 1 | LOAD TABLE CONVENTIONAL | T | | | | |
---------------------------------------------------------------------------------
Statistics
----------------------------------------------------------
71 recursive calls
9 db block gets
75 consistent gets
10 physical reads
1284 redo size
829 bytes sent via SQL*Net to client
785 bytes received via SQL*Net from client
3 SQL*Net roundtrips to/from client
9 sorts (memory)
0 sorts (disk)
1 rows processed
很顯然，由于ORA-28002錯誤導致了SET AUTOTRACE ON功能啟用時碰到了錯誤。當修改了當前的用戶密碼，則ORA-28002不再出現后，SET AUTOTRACE ON的功能恢復正常。
根據上面的信息其實可以判斷，在啟用SET AUTOTRACE ON功能時，sqlplus會自動創建一個新的會話來記錄當前會話的統計信息。
而啟用的新的會話會使用當前會話登錄時保存的密碼來進行登錄，因此可以通過下面的例子來驗證這個推論：
solaris*orcl-/home/oracle$ sqlplus test/test
SQL*Plus: Release 11.2.0.3.0 Production on Sun Jul 15 01:28:38 2012
Copyright (c) 1982, 2011, Oracle. All rights reserved.
Connected to:
Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - 64bit Production
With the Partitioning, Oracle Label Security and Real Application Testing options
SQL> set autot on
SQL> set autot off
SQL> alter user test identified by test1;
User altered.
SQL> set autot on
ERROR:
ORA-01017: invalid username/password; logon denied
SP2-0619: Error while connecting
SP2-0611: Error enabling STATISTICS report
果然，在用戶登錄后，如果當前的密碼被修改，是會導致SET AUTOTRACE ON啟用時報錯不正確的用戶名密碼錯誤的。