Oracle 9I新功能收缩表以节省空间（oracle9I收缩表）

Oracle 9I New Features: Table Compression for Space Savings

Oracle 9i introduced a new feature called table compression which allows users to compress data in their tables to save space. This feature is useful for those who have large databases that are affected by the increased amount of space required for storing data.

The concept of table compression is simple. It works by compressing data using an algorithm that reduces the amount of space required to store that data. This algorithm is called the Oracle Advanced Compression Algorithm (OACA), and it is used to determine how much space can be saved by compressing data in your database.

Here’s an example of how to use the Oracle 9i table compression feature. Let’s say you have a database table called Customers, which contns customer information such as their name, address, and phone number. You can compress this table using the following SQL statement:

ALTER TABLE customers COMPRESS FOR OLTP;

This statement compresses the Customers table using the OLTP (Online Transaction Processing) algorithm, which is designed for tables that see a lot of insert and update transactions. You can also use a different algorithm called the OLAP (Online Analytical Processing) algorithm, which is designed for tables used in data warehousing.

The advantages of using table compression are many. First, it saves disk space, which can be an important consideration for large databases. Second, it reduces the amount of time required for backups, since compressed data takes less time to back up. Third, it can improve query performance, since compressed data can be read from disk more quickly.

There are some potential drawbacks to using table compression, however. The first is that it can increase CPU usage, since compressing and decompressing data requires processing power. The second is that it can increase the time required for data inserts and updates, since compressed data takes longer to write. However, these drawbacks are usually outweighed by the benefits of using table compression.

In conclusion, Oracle 9i’s table compression feature is a useful tool for those who have large databases that require a lot of space. By compressing data using the OACA algorithm, you can save disk space, reduce backup times, and improve query performance. While there are some potential drawbacks to using table compression, they are generally outweighed by the benefits. If you are using Oracle 9i and have a large database to manage, you should consider using table compression to save space and improve performance.