oracle概念_分区

Partitions, Views, and Other Schema Objects

Partitioning enables you to decompose very large tables and indexes into smaller and more manageable pieces called partitions. Each partition is an independent object with its own name and optionally its own storage characteristics.

分区的优点

Increased availability
Easier administration of schema objects
Reduced contention for shared resources in OLTP systems
Enhanced query performance in data warehouses

Partition Key
用来决定分区的键值。
Partitioning Strategies
多种分区策略，可以只做一次分区，也可以分区之中再做分区。
用范围分区，用指定值list分区，用hash分区。

Index一样可以分区：
local partitioned index：一个索引的分区对应一个表的分区。
local partitioned index可以分为Local prefixed indexes和Local nonprefixed indexes。
Local prefixed indexes：The partition keys are on the leading edge of the index definition.
Local nonprefixed indexes： The partition keys are not on the leading edge of the indexed column list and need not be in the list at all.
注意查询的时候，可以对Local prefixed indexes做优化，partition elimination。

Global Partitioned Indexes
索引的分区和表的分区没有了一一对应关系。


Overview of Sequences
A sequence is a schema object from which multiple users can generate unique integers. A sequence generator provides a highly scalable and well-performing method to generate surrogate keys for a number data type.




Overview of Synonyms

A synonym is an alias for a schema object.

You can create both private and public synonyms. A private synonym is in the schema of a specific user who has control over its availability to others. A public synonym is owned by the user group named PUBLIC and is accessible by every database user.

Synonyms themselves are not securable. When you grant object privileges on a synonym, you are really granting privileges on the underlying object. The synonym is acting only as an alias for the object in the GRANT statement.