1. Briefly describe the composition of the Oracle database architecture.
Answer:
(1) Oracle database architecture consists of physical storage structure, logical storage structure and instances.
(2) The physical storage structure describes the storage and management of the operating system level data, including data files, log files, and redo log files.
(3) The logical structure describes the organization and management of the internal data of the database, which is composed of table spaces, segments, areas, and blocks.
(4) An instance is the software structure of the database running, which consists of a memory structure and background processes.
(5) During the operation of the database, user operations are performed in the memory area, and finally converted into operations on the database through the background.
3. The composition and relationship of the logical storage structure of the Oracle database.
Answer:
(1) The logical storage structure of Oracle database is divided into four types: Oracle data block, area, segment and table space.
(2) One or more continuous Oracle data blocks constitute an area, one or more areas constitute a segment, one or more segments constitute a table space, and all table spaces constitute a database.
9. Briefly describe the basic structure of the data dictionary.
Answer:
Static data dictionary table
Static data dictionary view
Dynamic data dictionary table
Dynamic data dictionary view
1. Explain the types of table spaces and the role of different types of table spaces.
Answer:
(1) Database table spaces are divided into two types: system table spaces and non-system table spaces. Non-system table spaces include undo table spaces, temporary table spaces, and user table spaces.
(2) The system table space is mainly used to store the data dictionary of the database, the source code and interpretation code of the PL/SQL program, and the definition of database objects.
(3) The revocation table space specializes in automatic management of rollback information. Temporary table space is a table space dedicated to temporary segment management.
(4) The user table space is used to separate data from different applications, and can reduce I/O conflicts when reading data files.
2. Explain the relationship between databases, table spaces, data files, and database objects.
Answer:
(1) A database is composed of one or more table spaces. Different table spaces are used to store data for different applications. The size of the table space determines the size of the database.
(2) A table space corresponds to one or more data files, and the size of the data file determines the size of the table space.
(3) A data file can only belong to one table space.
(4) A database object can only be stored in one table space, but it can be stored in one or more data files corresponding to the table space.
2. Briefly describe the types and functions of constraints in the table.
Answer:
(1) Primary key constraint: The value of the column that defines the primary key constraint cannot be empty or repeated.
(2) Unique value constraint: The value of the column that defines the unique value constraint cannot be repeated.
(3) Check constraint: the column value that defines the check constraint must meet the check condition.
(4) Foreign key constraint: The column value that defines the foreign key constraint is either the value of the reference column of the main table or the null value.
(5) Non-null constraint: the value of the column that defines the non-null constraint cannot be null.
5. Briefly describe the function of the sequence and how to use it.
Answer:
(1) A sequence is a database object used to generate a unique serial number. It can generate consecutive integers that are not repeated for multiple database users in sequence. Usually, the sequence is used to automatically generate the primary key value in the table.
(2) After the sequence is created, the sequence value can be generated through the sequence NEXTVAL attribute, and the current sequence value can be viewed through the attribute CURRVAL.
6. What are the advantages and partitioning methods of the partition table?
Answer: Advantages:
(1) Improve data security, the damage of one partition does not affect the normal use of data in other partitions;
(2) Store each partition of the table on different disks to improve the parallel operation capability of data;
(3) ) To simplify data management, some partitions can be set to unavailable state, some partitions are set to available state, some partitions are set to read-only state, and some partitions are set to read-write state;
(4) Operation transparency , Partitioning the table does not affect the SQL statement that manipulates the data.
The partitioning methods include: range partitioning, list partitioning, hash partitioning, and composite partitioning.
1. What are the security mechanisms of the Oracle database?
Answer: User management, authority management, role management, profile management, database auditing.
2. What kinds of permissions are available in the Oracle database?
Answer:
(1) There are two types of permissions in the Oracle database, system permissions and object permissions.
(2) System authority refers to the authority to perform a certain operation at the database level, or the authority to perform a certain operation on a certain type of object.
(3) Object authority refers to the authority to perform a certain operation on a particular database object. For example, permissions to insert, delete, modify, and query specific tables.
6. Briefly describe the role of the profile in the Oracle database?
Answer: It is mainly used to restrict users' use of database and system resources, and to manage user passwords.