oracle different table spaces

Oracle is a popular relational database management system. In its huge database, it is likely to need to use different table spaces to allocate storage space. Therefore, this article will focus on the use of different table spaces in Oracle.

First of all, we need to know what a table space is. In Oracle database, table space is a logical storage unit and can be regarded as a container for data storage. Tablespaces help manage and organize data files and can combine multiple data files to provide efficient management and help reduce the risk of data loss. Each table space contains one or more data files, and each data file saves data and table indexes.

Table spaces in Oracle databases are usually divided into two types: temporary table spaces and permanent table spaces. Permanent table spaces include SYSTEM table space, SYSAUX table space, UNDOTBS table space, user table space, etc.; temporary table spaces only include TEMP table space. So what is the role of each table space?

1. SYSTEM table space

The SYSTEM table space is one of the basic components of the Oracle database. It mainly stores system data and metadata (such as data dictionary views, system constraints etc.) and database kernel code. In addition, constants and fixed internal information used in SQL statements and stored procedures are also stored.

Since critical system data is stored in the SYSTEM table space, it is very important to manage and maintain it. To avoid excessive expansion of the SYSTEM table space, you can store custom objects (such as tables, indexes, etc.) in other user table spaces.

2. SYSAUX table space

The SYSAUX table space is the auxiliary table space of the database. It is mainly used to store some auxiliary system tables, views, stored procedures, and PL/SQL. Packages, information management tools, etc. In Oracle 10g and later versions, some newly added data dictionary views are also stored in the SYSUAX table space.

Because the objects in the SYSAUX table space are related to database operation, they cannot be DROP (delete), and only their storage parameters can be modified. Based on this, this table space is not mandatory to create, but in some cases it will be automatically created and used to store some new system objects.

3. UNDOTBS table space

In Oracle database, UNDO table space is a special table space used to manage data rollback. In some transactions, if problems occur (such as program crashes, power outages, and other unexpected situations), the transaction needs to be rolled back. This tablespace acts as a data buffer, recording all modifications made during transaction execution into a rollback segment, and restoring the original data during a rollback operation.

Unlike other table spaces, the size of the UNDOTBS table space should be more than twice the size of all user table spaces. Therefore, in systems with high memory requirements, it is necessary to fully consider the appropriate size of the UNDOTBS table space and make corresponding adjustments and optimizations.

4. TEMP table space

TEMP table space is a space specially used to store temporary data. Through the TEMP table space, operations that require a large amount of temporary space, such as sorting and creating intermediate tables, can be separated from other table spaces to avoid taking up too many resources and affecting other business operations.

It should be noted that the data in the TEMP table space is not permanent, so there is no need to perform operations such as backup and recovery.

5. User table space

The user table space is the main storage area for user-created tables and indexes in the Oracle database. When creating a database, the user tablespace is generally not automatically created. When creating a user, it needs to be set manually.

When creating a user table space, you need to determine its disk space size, block size, expansion strategy and other parameters. As the business expands, the amount of access to the user table space will become larger and larger, so it needs to be managed and optimized intensively.

In short, in Oracle database, table space is a very important concept, and its good management and maintenance can help improve the performance and reliability of the system. Therefore, when creating and using an Oracle database, it is necessary to carefully consider the rationality of each table space and make timely optimization and adjustments.

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