A Complete Guide to Modifying NLS_LANGUAGE in Oracle Database

Introduction

The NLS_LANGUAGE parameter is a crucial setting in Oracle Database that determines how the database displays language-specific information such as day and month names, error messages, and sort order. This guide will walk you through various methods to modify this parameter, along with best practices and troubleshooting tips.

Understanding NLS_LANGUAGE

Before diving into the modification methods, it’s essential to understand what NLS_LANGUAGE controls:

• Day and month names
• Error messages
• Various language-specific abbreviations
• Sort order for character data
• Default linguistic sorting sequence

Methods to Modify NLS_LANGUAGE

1. Session-Level Modification

The quickest way to change NLS_LANGUAGE is at the session level. This method affects only your current session and reverts when you disconnect.

ALTER SESSION SET NLS_LANGUAGE = 'AMERICAN';

Advantages:

• Immediate effect
• No restart required
• Doesn’t affect other users
• No special privileges needed (beyond ALTER SESSION)

2. System-Level Modification

For permanent changes affecting all database sessions, modify at the system level:

ALTER SYSTEM SET NLS_LANGUAGE = 'AMERICAN' SCOPE = SPFILE;

Important Notes:

• Requires SYSDBA privileges
• Database restart required
• Affects all users
• Should be planned during maintenance window

3. Environment Variable Method

Set the NLS_LANG environment variable in your operating system:

# Unix/Linux
export NLS_LANG=AMERICAN_AMERICA.AL32UTF8

# Windows (Command Prompt)
set NLS_LANG=AMERICAN_AMERICA.AL32UTF8

4. Configuration File Method

Add or modify the parameter in init.ora or spfile.ora:

NLS_LANGUAGE = AMERICAN

Commonly Used Language Values

Verification and Troubleshooting

Checking Current Settings

To verify your current NLS_LANGUAGE setting:

-- Check session parameters
SELECT * FROM NLS_SESSION_PARAMETERS WHERE PARAMETER = 'NLS_LANGUAGE';

-- Check database parameters
SELECT * FROM NLS_DATABASE_PARAMETERS WHERE PARAMETER = 'NLS_LANGUAGE';

Common Issues and Solutions

1. Invalid Language Error

   • Ensure the language code is valid
   • Verify correct spelling and capitalization
   • Check Oracle’s supported language list

2. Changes Not Taking Effect

   • Confirm proper privileges
   • Verify database restart after system-level changes
   • Check for overriding environment variables

3. Character Set Mismatches

   • Ensure NLS_LANG matches database character set
   • Verify client-side character set compatibility

Best Practices

1. Testing

   • Always test language changes in a development environment first
   • Verify application compatibility with new language settings
   • Document all changes and their effects

2. Change Management

   • Plan system-level changes during maintenance windows
   • Notify users before making global changes
   • Keep backup of original settings

3. Performance Considerations

   • Monitor system performance after changes
   • Consider impact on sorting operations
   • Evaluate effect on application caching

Conclusion

Modifying NLS_LANGUAGE is a straightforward process, but it requires careful consideration of the impact on your database environment. Choose the appropriate modification method based on your needs, following best practices and proper testing procedures to ensure a smooth transition.

Remember that language settings can significantly affect how your application presents information to users, so thorough testing in a non-production environment is essential before implementing changes in production.