Modify oracle encoding

With the upgrade of a large number of applications and data migration, we have more and more needs to change the character set in the Oracle database. Before modifying the encoding of the Oracle database, we need to consider some important issues, such as: the character set of the database, the new character set to be used, whether the data in the database needs to be converted, how to handle stored procedures, triggers, etc.

In Oracle database, we can modify its encoding through the following steps.

1. Determine the current character set and version

Before making encoding modifications, we first need to understand the character set and version of the current database. You can query it through the following command:

select * from nls_database_parameters;

This command will return the character set, language, date format and other parameters of the database.

2. Back up the database

Before making any database modifications, be sure to back up the database to prevent data loss or irrecoverability. We can use the data export tool (exp) provided by Oracle or the backup tool (rman) that comes with the Oracle engine for backup.

3. Create a new character set

Before modifying the encoding of the Oracle database, you need to create a new character set in the database. This character set should have properties for the new character set to be used for the database. In Oracle, we can use the charset command to create this character set.

CREATE CHARSET my_charset
    BASESET latin1
    ATTRIBUTE NEW_LEXEME_SCALE = 20;

In this example, we create a character set called "my_charset", using the Latin1 character set as the base, and set the new vocabulary scale attribute to 20.

4. Create a conversion table

Before making encoding modifications to the Oracle database, we need to create a conversion table in the database to convert the data in the original character set to New character set. In Oracle, we can use the CREATE CONVERT command to create a conversion table.

CREATE CONVERT my_conversion
    USING my_charset
    FROM original_charset;

In this example, we create a conversion table named "my_conversion", using the new character set (my_charset) and the original character set (original_charset).

5. Modify the database character set

After creating the new character set and conversion table, we can start to modify the encoding of the Oracle database. In Oracle, we can use the ALTER DATABASE command to modify the character set of the database.

ALTER DATABASE CHARACTER SET my_charset;

In this example, we change the character set of the database to the new character set "my_charset".

6. Convert data

After making encoding modifications to the Oracle database, we need to convert the data in the original character set to the new character set. In Oracle, we can use the CONVERT command to perform data conversion.

ALTER TABLE t1
    MODIFY (c1 CHAR(10) CHARACTER SET my_charset);

In this example, we use the ALTER command to change the character set of column c1 of the table named t1 to the new character set "my_charset".

7. Update stored procedures and triggers

After making coding changes to the Oracle database, we also need to update stored procedures and triggers. This is because stored procedures and triggers may contain references to the original character set. We need to go through all stored procedures and triggers and change the parts of them that reference the original character set to the new character set.

8. Complete Modification

After completing all the above steps, we can restart the Oracle database to integrate the new character set and conversion table with the old character set and data Reload into the database.

Summary

Modifying the Oracle database encoding is not a simple process. Before doing this, you must back up your database and know the character set and version of your current database. You also need to create new character sets and conversion tables to convert the data, and update stored procedures and triggers. Correct coding modifications can not only maintain data integrity but also improve application performance.

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