Oracle Lock
http://download-uk.oracle.com/docs/cd/B10501_01/server.920/a96524/c21cnsis.htm#2937
Types of Locks
Oracle automatically uses different types of locks to control concurrent access to data and to prevent destructive interaction between users. Oracle automatically locks a resource on behalf of a transaction to prevent other transactions from doing something also requiring exclusive access to the same resource. The lock is released automatically when some event occurs so that the transaction no longer requires the resource.
Throughout its operation, Oracle automatically acquires different types of locks at different levels of restrictiveness depending on the resource being locked and the operation being performed.
Oracle locks fall into one of three general categories.
LockDescription
DML locks (data locks)
DML locks protect data. For example, table locks lock entire tables, row locks lock selected rows.
DDL locks (dictionary locks)
DDL locks protect the structure of schema objects--for example, the definitions of tables and views.
Internal locks and latches
Internal locks and latches protect internal database structures such as datafiles. Internal locks and latches are entirely automatic.
The following sections discuss DML locks, DDL locks, and internal locks.
DML Locks
The purpose of a DML (data) lock is to guarantee the integrity of data being accessed concurrently by multiple users. DML locks prevent destructive interference of simultaneous conflicting DML or DDL operations. For example, Oracle DML locks guarantee that a specific row in a table can be updated by only one transaction at a time and that a table cannot be dropped if an uncommitted transaction contains an insert into the table.
DML operations can acquire data locks at two different levels: for specific rows and for entire tables.
Row Locks (TX)
The only DML locks Oracle acquires automatically are row-level locks. There is no limit to the number of row locks held by a statement or transa
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oracle表空间操作详解
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3作者： 来源： 更新日期：2006-01-04
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7建立表空间
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9CREATE TABLESPACE data01
10DATAFILE '/ora ......
// 建立表空间（指定文件路径）。
create TABLESPACE EAS_D_sptcc0_STANDARD DATAFILE 'F:\oracledb\EAS_D_sptcc0_STANDARD.dbf' size 10000M EXTENT MANAGEMENT local;
// 删除表空间（指定文件路径）。
DROP TABLESPACE temp_data INCLUDING CONTENTS AND DATAFILES;
// 建立临时表空间。
CREATE TEMPORARY TABLESPA ......
原文:http://www.blogjava.net/Unmi/archive/2009/01/05/249956.html
在 Oracle 数据库中，我们通常在不同数据库的表间记录进行复制或迁移时会用以下几种方法：
1. A 表的记录导出为一条条分号隔开的 insert 语句，然后执行插入到 B 表中
2. 建立数据库间的 dblink，然后用 create table B as select * from A ......
1、查看表空间的名称及大小
select t.tablespace_name, round(sum(bytes/(1024*1024)),0) ts_size
from dba_tablespaces t, dba_data_files d
where t.tablespace_name = d.tablespace_name
group by t.tablespace_name;
2、查看表空间物理文件的名称及大小
select tablespace_ ......
-- 查看ORACLE 数据库中本用户下的所有表
SELECT table_name from user_tables;
-- 查看ORACLE 数据库中所有用户下的所有表
select user,table_name from all_tables;
-- 查看ORACLE 数据库中本用户下的所有列
select table_name,column_name from user_tab_columns;
-- 查看ORACLE 数据库中本用户下的所有列
se ......
