Working with database concurrency can be tricky, especially when dealing with multi-user environments. Today, I'll walk you through Uniface'slock statement, a powerful tool for managing database occurrence locking.This article was created with the assistance of AI and is based on the Uniface Documentation 10.4.

🎯 What is the Lock Statement?

Thelock statement in Uniface locks the database occurrence of the current occurrence, ensuring that only the current process can modify it. This is crucial for maintaining data integrity in concurrent environments.

📊 Return Values and Status Codes

Understanding the return values is essential for proper error handling. Here's what you need to know:

💚 Success and Common Status Values

🚨 Error Handling with $procerror

The$procerror variable provides additional error information:

• -1 (UGENERR_ERROR): General error occurred
• -2 (UIOSERR_OCC_NOT_FOUND): Occurrence or record not found
• -2 through -12 (UIOSERR_*): Database I/O errors
• -16 through -30 (UNETERR_*): Network I/O errors

💡 Practical Example

Here's a practical example of how to use thelock statement with proper error handling:

trigger lock lock if ($status = -10) reload endifend; lock

This example demonstrates a common pattern: attempting to lock a record and reloading it if it has been modified since the last retrieval.

🔧 Important Considerations

🎭 DBMS Support

Keep in mind that if your DBMS doesn't support database locking or uses optimistic locking, thelock statement will be ignored. This makes it safe to use across different database systems.

📋 Component Compatibility

Thelock statement is allowed in all component types, making it versatile for various application scenarios.

🎯 Best Practices

• Always check the return status 📊 - Don't assume the lock was successful
• Handle the -10 status code 🔄 - Reload data when it has been modified
• Consider your DBMS 🗃️ - Understand how your database handles locking
• Test concurrent scenarios 👥 - Verify behavior with multiple users

🎉 Conclusion

The Unifacelock statement is a powerful tool for managing database concurrency. By understanding its return values and implementing proper error handling, you can build robust applications that handle multi-user scenarios gracefully.

Remember to always test your locking logic in environments that simulate real-world concurrent access patterns!