"Oracle" Logical Structure (Tablespace→segment→extent→block)



First, the logical system structure diagram

　　

Two, the logical structure diagram composition Introduction

As can be seen from the table above, a database consists of multiple table spaces (tablespace), a table space consisting of multiple segments (segment), a segment consisting of multiple zones (extent), and a block consisting of multiple blocks.

In a database, undo and system Tablespace must exist.

　　As an example:

Say Zhang San is a farmer in the dam county, every year the harvest of rice must be placed in the county Granary Unified Management. Along with him there are John Doe, Harry and other rice-based farmers.

At first, the county granary assigned him a 5㎡ (block) to store him. Later, he applied for 5㎡ to the leader of the Granary. Who knows this year's big harvest, this 10 square meters of place is not enough for him to use, next time apply for 5㎡. These three or two days will be a few places to put rice, the leadership feel bored, so go not to leave me busy dead? So the leader approved Zhang San can apply for 90㎡(extent district), so that Zhang San can be less annoying leaders to place rice. But with the Zhang San of a year and a year, the harvest of rice more than a year, 90㎡ is not enough for his use, so he applied to the leadership, but this time he was more relaxed, only to once, 90㎡ on the hand ... But soon, Zhang San's business has grown rapidly, with more than one kind of paddy, and an apple! He used the same way to apply for a 90㎡ place to put apples, and then the next year the business increased the growing pineapple ... In this way has been developed, Zhang San by the beginnings of his real harvest, the county's granary to his allotted place is not enough, Zhang San directly to the whole Granary (segment section) bought down, just reserve all the crops. But the next year, Zhang San has developed to the aquaculture industry, so directly beside himself built several warehouses, and to these warehouses (including the former Granary) a name, Mr. Zhang Warehouse (tablespace).

And John Doe, Harry also almost at the same time, also with Zhang San as wealthy, each also built their own warehouse, Mr. Li Warehouse (Tablespace1), Mr. Wang Warehouse (tablespace2) ...

The warehouses of their dozens of wealthy farmers formed a grain depot in the dam County.

Iii. Summary

　　For us to create a new database in the database, create more than one table space (tablespace)in the database, and build the table in each tablespace. For example, we can assign multiple users, under the User1 user to establish table1,table2,user2 under the establishment of Table3,table4,user1, User2 is equal to the different table space, Table1, Table2 is established in the table space under the different segments (segment), and each table data is block, a column of data can be regarded as a region (extent), the area is full after the expansion of the table.

For more information, see Harvest, more than Oracle, this article is for summary use only, please correct if there are errors.