SQL Server’s Contained Databases: Simplifying Database Administration
Introduction to Contained Databases
As databases become more central to the operations of businesses, the necessity for efficient and more isolated management of these data repositories becomes paramount. Enter Contained Databases in SQL Server – a feature designed to make the lives of database administrators and developers easier. Contained databases are essentially databases that are isolated from the instance of SQL Server that host them, ensuring that the configuration of one database does not affect others or the underlying instance. This characteristic enables the movement of databases with ease and reduces the complexities associated with database administration such as managing many databases across various environments. This article provides a comprehensive analysis of contained databases, exploring their benefits, how they work, and their implications for database administration.
What Are Contained Databases?
A contained database is a database that is isolated from the environment in which it resides. Unlike traditional databases, contained databases include all the necessary settings and metadata within the database itself rather than in the master databases or the instance of SQL Server. This isolation means that the database is not dependent on the instance-level settings, making it easy to migrate from one server to another. At its core, the concept of a contained database addresses the problems associated with database portability and the ‘spaghetti’ of dependencies that can occur in complex SQL Server environments.
Advantages of Using Contained Databases
1. Simplified Database Management
The autonomy of contained databases drastically simplifies database management. Administration tasks such as backup, restore, and moving databases become less cumbersome as the databases are self-contained. Additionally, this facilitates better organization and allows for databases to be treated as a single unit, without worrying about dependencies on the server where it is hosted.
2. Enhanced Portability
One of the primary benefits is the ease with which a contained database can be moved or copied to another instance of SQL Server. This simplification diminishes concerns about whether the new environment has compatible configuration settings, making deployment processes more robust and less error-prone.
3. Streamlined Deployment and Migration
Deploying and migrating SQL Server databases between different environments (development, testing, production) is traditionally a complex task that requires a deep understanding of each environment’s configuration. Contained databases facilitate these processes by cutting out the necessity to configure the external components, saves time and effort significantly during the deployment or migration process.
4. Isolation from Instance-Level Changes
Contained databases isolate the database from instance-level setting changes, which can be quite beneficial. Changes at the SQL Server instance level can have unintended consequences on databases. When using contained databases, these risks are minimized because their settings are self-contained.
5. Simplified User Management
In a traditional SQL Server environment, logins are created at the instance level, which creates a tight coupling between databases and the server instance. Contained databases, however, support contained users, which are users defined within the database itself. This feature allows database users to access the database without an associated server-level login, leading to better security and easier user management.
Understanding the Technology Behind Contained Databases
The separation between the database and the instance is accomplished by embedding certain instance-level metadata within the database. This includes but is not limited to, the default collation settings for the database, language settings, the credentials of contained users, and any custom error messages.
Contained Database Types
SQL Server supports two types of contained databases:
- Partially Contained Databases: This is the most widely used type. They aim to reduce many of the dependencies on the instance but do not eliminate all of them. Here, you still might have some dependencies such as linked servers or cross-database queries.
- Fully Contained Databases: These databases are completely isolated from their instance in every manner. Unfortunately, as of the knowledge cutoff date, SQL Server does not yet support fully contained databases, but the concept represents the end-goal for contained database technology.
Login and User Management Differences
In a contained database, contained users are authenticated directly within the database, bypassing the server logins. This approach differentiates the administrative boundaries between the instance and the database, providing a more granular control over access rights and security within the database.
Steps to Enable Contained Databases in SQL Server
Enabling Contained Databases at the Instance Level
Before you can create a contained database, you must first enable the feature at the SQL Server instance level. This can be done either through SQL Server Management Studio or with Transact-SQL:
EXEC sp_configure 'show advanced options', 1;
RECONFIGURE;
EXEC sp_configure 'contained database authentication', 1;
RECONFIGURE;
This script enables the advanced options and sets the contained database authentication option to true. Following this, the SQL Server instance will need a restart for the changes to take effect.
Creating a Contained Database
Creating a contained database is done similarly to creating any other SQL Server database, with a few additional steps:
CREATE DATABASE DatabaseName
CONTAINMENT = PARTIAL;
GO
Additionally, to convert an existing database to a contained database, you can use the following Transact-SQL command:
ALTER DATABASE DatabaseName
SET CONTAINMENT = PARTIAL;
GO
The procedure above is straightforward and allows for quick conversion from traditional to contained databases.
Migrating to Contained Databases:
1. Planning and Assessment
Before moving to contained databases, it is crucial to assess your current database and instance setup. You need to identify any external dependencies such as: cross-database queries, server-level triggers, and linked servers. Documentation and comprehensive analysis of the current setup will be crucial for a smooth migration process.
2. Pre-migration Testing
After the assessment and planning, it’s recommended to rigorously test the migration in a controlled environment. This will help to catch any potential issues that could arise due to the containment and rectify them before moving to production.
3. Migration Procedure
Once the testing is complete and you’re satisfied with the results, the actual migration can be performed. Changing the containment setting of a database, updating user accounts to contained users, and ensuring that all your applications correctly point to the new setup are all parts of this process.
4. Monitoring and Validation
Post-migration, it is vital to monitor the performance and behavior of the contained databases closely. There could be a need for changes in indexing, query optimization or other performance aspects that are only apparent after full-scale deployment.
Considerations and Best Practices
Security Implications
When dealing with contained databases, it is vital to emphasize security. Ensuring strong passwords for contained users and understanding the scope of permissions within the database is crucial because these users do not have linked server logins to provide an additional layer of security.
Database Compatibility Levels
Contained databases function within specific database compatibility levels. When enabling containment on an existing database, checking its current compatibility level and adjusting it if necessary to ensure proper function within a contained environment is important.
Backup and Disaster Recovery Strategies
Backup and disaster recovery strategies need to account for the self-contained nature of the databases. Strategies need to be revisited to ensure that they still meet recovery objectives when dealing with contained databases. Backup restoration procedures might also be modified in line with contained database behaviors.
Taking Advantage of Performance Isolation
Contained databases can offer greater levels of performance isolation, which can allow for targeted tuning and optimization. It is essential to use performance isolation to your advantage by being able to fine-tune individual databases without impacting others.
Future Directions and Updates
Microsoft continually evolves SQL Server, and contained databases represent a dynamic feature that is likely to see further enhancements. Keeping abreast of new updates and how they may affect or improve your database setup will be critical.The potential realization of fully contained databases may revolutionize the ease with which multi-environment deployment and isolated database administration is handled.
Conclusion
Contained databases in SQL Server offer a plethora of advantages that can simplify database administration. Their isolation from the instance environment and their portability makes deployment, management, and migration straightforward and more secure. While they signify an efficient and innovative solution, being aware of the full implications, from alignment with established practices to compatibility and security considerations, is essential. As SQL Server evolves and moves closer to the ideal of fully contained databases, administrators and developers alike should stay informed and equipped to leverage these advantages fully.
