"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.

　　To give a sample 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 the beginning of the county, the Granary assigned him a 5㎡ place (block blocks) for him to store. 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 thought bored, so do not keep me busy to die? So the leader approves Zhang San can apply 90㎡(extent area)once, this kind of words Zhang San can be less to annoy the leader to place Paddy. But with the Zhang San year by year, the harvest of rice is more than a year, 90㎡ is not enough for him to use, so he applied to the leadership, but this time he was more relaxed, just went once, 90㎡ on hand ... But very quickly, the business of Zhang San Rapid development, has been more than kind of rice, but also planted apples! He used the same way to apply for a 90㎡ place to put apples, and then the next year to add a business to grow 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 Granary before) a name, Mr. Zhang Warehouse (tablespace).

And John Doe, Harry also nearly 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 multiple table spaces (tablespace)in the database, and build tables in each table space. For example, we can assign multiple users, under the User1 user set up 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 of data is block, a column of data can be regarded as a region (extent), the area is full after the expansion of the table formed.