Oracle Database Structure Overview (1)

Introduction: ORACLE DatabaseIt contains several data files and data files to store database data, including tables and indexes. For many beginners who do not know much about Oracle databases, the next step is to start learning from the basics.
I. Physical Structure:

1. Data Files

The ORACLE Database contains several data files, which store database data, including tables and indexes. Several data filesFeatures:

1) only one data file can be allocated to one database.

2) data files can be set to automatically scalable

3) one or more data files form tablespaces

During database operations, the database first looks for the data to be operated from the memory. If no data is found, it then retrieves the data from the data file and stores it in the memory, then perform operations on the data in the memory. The operated data is not immediately written to the data file (which reduces disk I/O), but stored in the memory. Then, the DBWn process determines when to write data files in batches.

2. Control File

Each database has one or more control files. The control file containsPhysical Structure, Including:

1) Database Name

2) data file name and location

3) redo log file name and location

4) database creation time and so on

Generally, a database has several control file images. When the database is opened (ALTER

Database open), read the information in the control file to OPEN the DATABASE. When the physical structure of the database changes, such as adding a data file and a group of redo logs, the control file is automatically modified accordingly. After the physical structure of the database changes, it is best to back up the control file again for database recovery.

3. redo log files

Data changes are recorded in the redo log. Generally, a database has two or three groups of redo log files. Images in the same log group are best distributed on different disks.

4. Archiving logs

When the database starts archiving, redo logs are automatically archived to the specified location.

5. initialize the parameter file

Contains the configuration information when the database is started.

6. Warning and tracking log files

1) Tracking file: each background process has a separate tracking file. For example, when the system finds a problem with a process, the relevant information will be written to the corresponding tracking file. You can find and debug database errors from database trace files.

2) Warning file, also known as warning log. It is a special tracking file that records information about database startup and running. It records data in chronological order.

7. Backup Files