10 Imp DMV/DBCC and System catalog views

 As a Database Administrator (DBA), utilizing Dynamic Management Views (DMVs) is essential for monitoring and maintaining SQL Server performance. Here are ten commonly used DMVs:

1. sys.dm_exec_sessions: Provides details about all active user connections and internal tasks, including session IDs, login names, and session statuses.

2. sys.dm_exec_requests: Displays information about each request executing within SQL Server, such as query text, execution status, and wait times.

3. sys.dm_exec_query_stats: Offers aggregate performance statistics for cached query plans, including execution counts, CPU usage, and I/O statistics.

4. sys.dm_exec_query_plan: Returns the execution plan for a query, aiding in performance tuning and optimization.

5. sys.dm_exec_connections: Provides information about active connections to the SQL Server instance, including client network address and protocol details.

6. sys.dm_os_wait_stats: Aggregates wait statistics, helping identify resource bottlenecks and performance issues.

7. sys.dm_os_performance_counters: Contains performance counter data collected by SQL Server, useful for monitoring system health and diagnosing issues.

8. sys.dm_db_index_usage_stats: Tracks how indexes are utilized, assisting in identifying unused or underused indexes.

9. sys.dm_db_missing_index_details: Provides information on missing indexes that could improve query performance.

10. sys.dm_tran_locks: Displays information about current locks, aiding in diagnosing blocking and deadlock issues.

Regularly querying these DMVs enables proactive monitoring and effective troubleshooting of SQL Server environments.

For a more in-depth understanding, you might find this video tutorial helpful:

As a Database Administrator (DBA), maintaining the health and performance of SQL Server databases is paramount. Utilizing Database Console Commands (DBCC) is essential for routine maintenance tasks. Here are five commonly used DBCC commands focused on database maintenance:

1. DBCC CHECKDB: Checks the logical and physical integrity of all objects in the specified database. It's advisable to run this command regularly to detect and repair corruption issues. citeturn0search1

   DBCC CHECKDB ('YourDatabaseName') WITH NO_INFOMSGS;
   

2. DBCC CHECKALLOC: Validates the consistency of disk space allocation structures for a specified database, ensuring that all pages are correctly allocated.

   DBCC CHECKALLOC ('YourDatabaseName') WITH NO_INFOMSGS;
   

3. DBCC CHECKTABLE: Examines the integrity of all pages and structures that make up a table or indexed view, useful for pinpointing issues within specific tables.

   DBCC CHECKTABLE ('YourDatabaseName.SchemaName.TableName') WITH NO_INFOMSGS;
   

4. DBCC DBREINDEX: Rebuilds one or more indexes for a table in the specified database, improving query performance by reducing fragmentation.

   DBCC DBREINDEX ('YourDatabaseName.SchemaName.TableName');
   

5. DBCC SHRINKDATABASE: Reduces the size of the data and log files in the specified database, freeing up space on the server.

   DBCC SHRINKDATABASE ('YourDatabaseName');
   

Regular execution of these commands helps ensure database integrity and optimal performance. It's important to schedule these operations during maintenance windows to minimize impact on users. Additionally, always ensure you have recent backups before performing maintenance tasks that modify database structures.

In SQL Server, catalog views provide essential metadata about various database components, aiding in effective database management and development. Building upon the previously mentioned views, here are additional catalog views, including sys.sysdatabases, that are particularly useful:

1. sys.sysdatabases: Contains a row for each database in the instance, providing details such as database name, ID, and status. Note that sys.sysdatabases is a legacy view; for newer applications, it's recommended to use sys.databases.

   SELECT * FROM sys.sysdatabases;
   

2. sys.sysobjects: Returns a row for each object (such as tables, views, procedures) in the database. This is a legacy view; the modern equivalent is sys.objects.

   SELECT * FROM sys.sysobjects;
   

3. sys.sysindexes: Provides information about indexes and tables stored in the database. This is a legacy view; the modern equivalent is sys.indexes.

   SELECT * FROM sys.sysindexes;
   

4. sys.syscolumns: Contains a row for each column in all tables and views. This is a legacy view; the modern equivalent is sys.columns.

   SELECT * FROM sys.syscolumns;
   

5. sys.sysusers: Lists all users in the database. This is a legacy view; the modern equivalent is sys.database_principals.

   SELECT * FROM sys.sysusers;
   

6. sys.syspermissions: Contains information about object-level permissions. This is a legacy view; the modern equivalent is sys.database_permissions.

   SELECT * FROM sys.syspermissions;
   

7. sys.sysfiles: Provides information about the database files. This is a legacy view; the modern equivalent is sys.master_files.

   SELECT * FROM sys.sysfiles;
   

8. sys.syslogins: Contains a row for each login account. This is a legacy view; the modern equivalent is sys.server_principals.

   SELECT * FROM sys.syslogins;
   

9. sys.sysconstraints: Provides information about constraints on tables. This is a legacy view; the modern equivalent is sys.check_constraints and sys.foreign_keys.

   SELECT * FROM sys.sysconstraints;
   

10. sys.sysreferences: Contains information about foreign key relationships. This is a legacy view; the modern equivalent is sys.foreign_keys.

    SELECT * FROM sys.sysreferences;
    

While these legacy views (sys.sys*) are available for backward compatibility, it's advisable to use the newer catalog views (sys.*) in modern applications for enhanced functionality and support.