How to Handle SQL Server Performance Problems Caused by Orphaned Users
Managing a SQL Server database involves ensuring solid security practices while maintaining optimal performance. A common yet often overlooked issue that can hamper both these aspects is the presence of orphaned users. These are database users that exist in the database but no longer have associated logins at the server level, often due to restored or moved databases. In this article, we’re going to explore the issue of orphaned users, its impact on performance, and the steps you can take to rectify this problem.
Understanding Orphaned Users in SQL Server
In the context of SQL Server, orphaned users occur when a database user is not properly associated with a corresponding login at the server level. This disassociation can happen when databases are moved from one server to another, backups are restored to a new server, or when logins are deleted without a corresponding user being removed from the database.
Before we delve into solutions, it’s crucial to understand what constitutes a user in SQL Server. A user is an account that resides within a specific database and has permissions to perform actions within that scope. A login, on the other hand, is an account that allows access to the SQL Server instance as a whole. Logins are associated with users at the database level to provide the necessary permissions. When this relationship becomes disjoined, we encounter the issue of orphaned users.
The Impact of Orphaned Users
Orphaned users might seem like a small issue, but they can lead to a number of problems, primarily in performance and security. Performance problems arise because SQL Server still spends resources maintaining the security principals for these orphaned users, despite their lack of active connections. Moreover, if applications are designed to interact with specific user accounts, the presence of orphaned users can create confusion and processing delays while the system resolves permissions.
In the realm of security, orphaned users represent potential vulnerabilities. If a new login is inadvertently associated with an orphaned user, it could unintentionally grant more privileges than intended. Regular maintenance to remove these orphaned users is not just about keeping the system tidy; it’s about maintaining its integrity and security posture.
Identifying Orphaned Users
Before we can rectify the problem of orphaned users, we need to identify them. SQL Server provides various methods to detect orphaned users:
USE [YourDatabaseName]
GO
EXEC sp_change_users_login 'Report'
GO
The sp_change_users_login stored procedure with the ‘Report’ argument can be used to find any orphaned users in a database. This should be among the first steps taken. Once you get the report, you can verify it against the list of logins in the server.
Additionally, some SQL scripts enable DBAs to check across multiple databases using system views such as sys.database_principals and sys.server_principals:
SELECT dp.name AS UserName, sp.name AS LoginName
FROM sys.database_principals dp
LEFT JOIN sys.server_principals sp ON dp.sid = sp.sid
WHERE dp.type = 'S' AND dp.principal_id > 4
AND sp.name IS NULL;
This script checks for users who do not have a matching SID (Security Identifier) at the server level. SIDs are unique identifiers for each login and user. When they don’t match up, it’s a clear sign of an orphaned user.
Fixing Orphaned Users
Once orphaned users are identified, there are several approaches to resolving the issue:
Re-create the user’s login with the same SID on the server.
Re-map the user to another existing login.
Delete the orphaned user if it’s no longer required.
To address orphaned users, SQL Server provides the sp_change_users_login stored procedure, which automates fixing orphaned users:
EXEC sp_change_users_login 'Auto_Fix', 'UserName', NULL, 'YourStrongPassword';
‘Auto_Fix’ will attempt to map the orphaned user to a login with the same name. If that login doesn’t exist, it will create one with the specified password. Always be cautious while using ‘Auto_Fix’ as it has the potential to grant permissions that you may not intend if not careful.
Beyond Orphaned Users: SQL Server Performance Tuning
While addressing orphaned users is important, there’s more to SQL Server performance tuning. It includes assessing and optimizing index strategies, monitoring and resolving bottlenecks in hardware resources, fine-tuning queries, and much more. Staying proactive with regular database maintenance, updating statistics, and monitoring will help keep SQL Server running at its best.
Effective SQL Server performance tuning involves:
- Regularly updating statistics and reorganizing indexes.
- Ensuring resource allocation is optimized.
- Analyzing and rewriting poor performing queries.
- Maintaining a well-organized database file structure.
- Using monitoring tools to catch problems early.
Monitoring Tools
SQL Server includes some integral tools for monitoring performance such as Dynamic Management Views (DMVs) and SQL Server Profiler. Third-party monitoring solutions can also offer more in-depth analysis and automation capabilities for larger environments.
Conclusion
The health and performance of a SQL Server environment can be significantly impacted by the presence of orphaned users. Identifying and resolving orphaned user issues is a critical step in overall SQL Server maintenance. Proactive approaches, combined with regular system checks, will go a long way toward ensuring that your databases are secure and performant. Remember, the goal is not just to fix issues as they arise, but to prevent them from occurring in the first place.
