Understanding several concepts of Oracle

I have learned several types of databases, such as mssqlserver and sqlite. Some basic logical and physical structures are similar. However, when I was in contact with oracle, I was confused about some concepts, here are some differences in the learning process:
1. After creating a user, the system will create a solution with the same name. The user has the permission to manage the database objects in the solution with the same name, at the same time, the system will create a default profile for the relevant vehicle (including a set of constraints and configuration items, which can limit the resources that can be used by users );

2. When creating a user, you must specify the user's default tablespace and temporary tablespace;

3. Different users have been created, and different schemes have been created, but the same tablespace can be specified for different users;

4. A tablespace is a logical storage unit. You can add one or more data files to a tablespace;
5. Create a data object in the solution, and the physical space of the database object is the user's default tablespace;

6. Multiple schemes can share one tablespace;
7. Sequence in oracle

The function of a sequence is to automatically generate an integer value as the value of the field identified in the table.

7.1 create sequence:

Createsequence userman. user_s

The minimum value of the Minvalue 1 sequence is 1.

The Nomaxvalue sequence has no maximum value limit.

The initial value of the Start with 1 sequence is 1.

Increment by 1 sequence interval is 1

Nocycle has no cyclic Value

Cache 20 indicates that the Cache is 20

7.2 use sequence

The same sequence generator can be used for one or more tables. The generated serial number can be used to generate a unique primary key.

User_s.nextval

Eg: Insertinto userman. users (user_id, user_name) values (userman. user_s.nextval, 'newuser ')

8. MGMT_user.make_em_user ('username ')

Configure the specified user to log on to the OEM