070109-1.Database Integration
The supplied PL/SQL package DBMS_RESOURCE_MANAGER lets the
database administrator create, update, and delete resource plans and resource
consumer groups. The administrator defines a user's default consumer group and
what privileges the user has (using the DBMS_RESOURCE_MANAGER_PRIVS
package). A user or session can switch resource consumer groups (using DBMS_
SESSION.SWITCH_CURRENT_CONSUMER_GROUP) to change execution priority, if
the user has been granted the privilege to switch to that consumer group.
（DBMS_RESOUCE_MANAGER包使管理员能够创建、更新、删除资源规划和资源消费组。定义一个用户的默认消费组及这个用户拥有的权限使用DBMS_RESOURCE_MANAGER_PRIVS包。一个用户或会话可以变换资源消费组通过使用DBMS_SESSION.SWITCH_CURRENT_CONSUMER_GROUP来改变执行的优先权，前提是这个用户已经被授予变换消费组的权限。）
0111-1.Introduction to Schema Objects
There is no relationship between schemas and tablespaces: a tablespace can contain
objects from different schemas, and the objects for a schema can be contained in
different tablespaces.
表空间与schemas之间没有关系：一个表空间可以包含来自不同的schemas的对象，同样schemas的对象也可以包含于不同的表空间。
To conserve space, a null in a column only stores the column length (zero). Oracle
does not store data for the null column. Also, for trailing null columns, Oracle does
not even store the column length.
为了节省空间，对于空列oracle仅仅存储列的长度（0），不存储空列的数据。而对于trailing null列oracle甚至不存储列的长度。
Rowids of Row Pieces
The rowid identifies each row piece by its location or address. After they are
assigned, a given row piece retains its rowid until the corresponding row is deleted
or exported and imported using the Export and Import utilities. For clustered
tables, if the cluster key values of a row change, then the row keeps the same rowid
but also gets an additional pointer rowid for the new values.
Rowid确定每个行块的位置或地址。一旦他们被赋予了某行的值，则这个行将保持这个Rowid直到相应的行被删除或导入、导出。对于簇表，如果某行的簇键值改变了，它仍然保持原来的rowid，但是也会增加一个额外的指针rowid用来记录新的值。
Nulls Indicate Absence of Value
Nulls indicate missing, unknown, or inapplicable data. A null should not be used to imply any other value,such as zero
Null就是缺少的，不知道的或者说是不能使用的数据。A null不能够等同于任意的其他的值比如说0。.
Nulls are stored in the database if they fall between columns with data values. In these cases they require 1 byte to store the length of the column (zero).
用一个字节来存储列的长度
Trailing nulls in a row require no storage because a new row header signals that the remaining columns in the previous row are null.
在一行中的末尾的空值不需要存储因为在下一个新的行头的标志中会记录前面一行的null值。
Nulls are not indexed, except when the cluster key column value is null or the index is a bitmap index.
Nulls值不会索引，除了簇的键值是空的或者索引是位图索引。
Temporary Tables
DML locks are not acquired on the data of the temporary tables. The LOCK statement has no effect on a temporary table, because each session has its own private data.
DML锁不会在临时表上使用。锁语句不会影响临时表，因为每个会话有它们自己私有的数据。
今天在PUB上逛了下感觉自己还是脚步速度太慢还要加快脚步！！！
