解决方法

sql> DROP SEQUENCE s ;

Sequence dropped.

sql>
sql> CREATE SEQUENCE s START WITH 500 INCREMENT BY 1;

Sequence created.

sql>
sql> DROP TABLE t PURGE;

Table dropped.

sql>
sql> CREATE TABLE t AS SELECT LEVEL id FROM dual CONNECT BY LEVEL < =20;

Table created.

sql>
sql> SELECT * FROM t;

        ID
----------
         1
         2
         3
         4
         5
         6
         7
         8
         9
        10
        11

        ID
----------
        12
        13
        14
        15
        16
        17
        18
        19
        20

20 rows selected.

sql>

sql> UPDATE t SET ID = s.nextval;

20 rows updated.

sql>
sql> SELECT * FROM t;

        ID
----------
       500
       501
       502
       503
       504
       505
       506
       507
       508
       509
       510

        ID
----------
       511
       512
       513
       514
       515
       516
       517
       518
       519

20 rows selected.

sql>

for each table in database
  for each row in table
    for each column in row
      if column is of type ''varchar2''
        column = trim(column)

解决方法

SET SERVEROUTPUT ON

BEGIN
  FOR c IN
    (SELECT t.table_name,c.column_name
       FROM user_tables t,user_tab_columns c
       WHERE c.table_name = t.table_name
         AND data_type=''VARCHAR2'')
  LOOP

    dbms_output.put_line(
                      ''UPDATE ''||c.table_name||
                      '' SET ''||c.column_name||'' = TRIM(''||c.column_name||'') WHERE ''||
                      c.column_name||'' <> TRIM(''||c.column_name||'') OR (''||
                      c.column_name||'' IS NOT NULL AND TRIM(''||c.column_name||'') IS NULL)''
                     );
  END LOOP;
END;

ODP.NET默认使用连接池.通常没有问题,但是当用户在连接错误后重试操作时,NHibernate从ODP.NET获取无效(池化)连接.用户必须重试多次(直到池为空)才能再次工作.

当然我可以禁用ODP.NET中的连接池,但是我想避免这种情况.我还读了一个设置,检查从池中每个返回的连接到DB的连接,但这又增加了我想避免的每个连接的一次往返.

有没有办法配置ODP.NET在任何连接引发连接异常时自动清除连接池？

The Validate Connection attribute validates connections coming out of the pool. This attribute should be used only when absolutely necessary,because it causes a round-trip to the database to validate each connection immediately before it is provided to the application. If invalid connections are uncommon,developers can create their own event handler to retrieve and validate a new connection,rather than using the Validate Connection attribute. This generally provides better performance.

如果它不够好 – 你可以尝试从oracle的this文档.

Connection Pool Management

ODP.NET connection pool management provides explicit connection pool
control to ODP.NET applications. Applications can explicitly clear
connections in a connection pool.

Using connection pool management,applications can do the following:

Note: These APIs are not supported in a .NET stored procedure. Clear
connections from connection pools using the ClearPool method.

Clear connections in all the connection pools in an application
domain,using the ClearallPools method.

When connections are cleared from a pool,ODP.NET repopulates the pool
with new connections that have at least the number of connections set
by Min Pool Size in the connection string. New connections do not
necessarily mean the pool will have valid connections. For example,if
the database server is down when ClearPool or ClearallPools is called,
ODP.NET creates new connections,but these connections are still
invalid because they cannot connect to the database,even if the
database comes up a later time.

It is recommended that ClearPool and ClearallPools not be called until
the application can create valid connections back to the database.
.NET developers can develop code that continuously checks whether or
not a valid database connection can be created and calls ClearPool or
ClearallPools once this is true.

另外,可能是this post会帮你的.

更新：
正如@Mpelletier所指出的那样,对于oracle 12 the link is different.

>它是否删除该特定用户使用的所有表空间和数据文件.
>如果没有,删除该特定用户使用的所有表空间/数据文件/磁盘空间的命令是什么.

DROP USER SAMPLE CASCADE;
ALTER TABLESPACE SAMPLE OFFLINE;
DROP TABLESPACE SAMPLE INCLUDING CONTENTS;
ALTER TABLESPACE SAMPLE_INDEX OFFLINE;
DROP TABLESPACE SAMPLE_INDEX INCLUDING CONTENTS;