online schema change

Online schema change refers to updating the structure of a database (such as adding a new table, altering columns, or changing indexes) without shutting down the entire system. This process allows the database to continue serving users and handling queries during the update, minimizing downtime. Techniques often involve creating a new version of the structure alongside the existing one, gradually migrating data, and then switching over seamlessly. This approach ensures continuous availability and reduces impact on users while maintaining data integrity throughout the change process.