Having the client close to the server in geographical proximity is important. However, this is not as important of having the database closer to the server.
In SSMS, we many of may noticed System Databases under the Database Folder. But how many of us knows its purpose?. In this article lets discuss about the System Databases in SQL Server.
Fig. 1 System Databases
There are five system databases, these databases are created while installing SQL Server.
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The SQL Server design implies a one-to-many mapping between the database engine (instance) and the databases hosted on the instance. It means that you can deploy several databases on one instance of the SQL server. According to the Microsoft documentation, you can have up to 32767 databases on a single instance of SQL Server. Of course, there will be limitations, like the resources on the server, managing concurrency on TempDB, network traffic, etc.
Databases deployed on a SQL Server instance can either be System Databases or User Databases. System Databases come installed with the instance. In this article, we will discuss the purpose of each System database. Also, we’ll clarify what you need to care for when managing system databases on SQL Server.
System databases are a part of many processes taking place when you install an instance of SQL Server. By default, these databases are created in the following paths:
%programfiles%\Microsoft SQL Server\MSSQL15.MSSQLSERVER\MSSQL\DATA
%programfiles%\Microsoft SQL Server\MSSQL15.MSSQLSERVER\MSSQL\Log
The path can be different. During the installation of SQL Server, you can specify the location of the system database files.
To list all the system databases in an instance, you can invoke the code in Listing 1. Listing 2 can be used to determine the location of the datafiles associated with the system databases. Note that in both scripts, we use a filter returning databases with database_id of 5 or higher than 5.
The essential “visible” system databases have database_ids 1,2,3,4 – they refer to master, tempdb, model, and msdb, respectively. There is also an “invisible” database called the resource databases and other system databases created when you enable features like replication.
-- Listing 1: System Databases select name ,database_id ,create_date ,state_desc ,recovery_model_desc ,log_reuse_wait_desc ,physical_database_name ,is_db_chaining_on ,is_broker_enabled ,is_mixed_page_allocation_on from sys.databases where database_id<5; -- Listing 2: System Database Files select name ,database_id ,DB_NAME(database_id) ,name ,physical_name ,type_desc from sys.master_files where database_id<5;
Figure 1: System Databases
The master database is the first database open on the start of SQL Server, containing the following data:
Thus, it has the information necessary for opening all other databases. That’s why it has to be first to open. The question is how to do it.
The SQL Server startup parameters contain two entries, which define the locations of the master database data and log files. The default startup parameters include only three lines – the third one is the error log file location. When SQL Server starts up, it must be able to write to that error log file.
The master database opens first. The information stored in the master database, including the configurations defined using sp_configure, applies to open other databases and complete the instance startup process.
Figure 2: SQL Server Configuration Manager
Figure 3: SQL Server Startup Parameters
There are several ways to learn about useful SQL Server system objects, like Dynamic Management Views and Functions.
For instance, expand the views or programmability nodes for the master database on object explorer. There, review these objects’ names and get more details from Books Online.
You can also migrate logins from one instance to another. For that, restore a backup of the master database to the destination instance. We’ll describe the specific technique in a separate article.
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When working in the SQL Server, we may have to check some other databases other than the current one which we are working. In that scenario we may not be sure that does we have access to those Databases?. In this article we discuss the list of databases that are available for the current logged user in SQL Server
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This is part 3 of “MS SQL Server- Zero to Hero” and in this article, we will be discussing about the SCHEMAS in SQL SERVER. Before getting into this article, please consider to visit previous articles in this series from below,
In part one, we learned the basics of data, database, database management system, and types of DBMS and SQL.
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The master database contains records of the structure/configuration for both the current instance and all other databases. When you run sp_configure, you are writing data to the master database. It also contains most of the dynamic management views that are necessary to monitor the instance.
The importance of the master database is crucial. First, it has the information necessary for opening all other databases and has to be opened first. Then, it involves all instance level principals for the current instance.
It is crucial to back up the master database daily. Equally important is to know how to restore the master database to the instance. The most frequent cases are the database crash or the necessity to restore the master database to another instance when no longer use the source instance. In this article, we will examine the specific case of moving the master database to another instance.
Restoring the master database to another instance will involve starting the instance in the single user mode. Thus, it is essential to make sure that the active session is the only one controlling the instance.
For that, stop all application services from accessing the instance, especially if such applications have privileged access. Problems can occur if you start the instance in the single-user mode while the application has already established a session. In this case, you will not be able to proceed with an interactive session from SQL Server Management Studio.
Stop all SQL Server Services with the SQL Server Configuration Manager: right-click each service and select Stop from the context menu (see fig. 2).
Figure 1. Stopping SQL Services
To restore the master database, you need the SQL Server instance in the single user mode. Take the following steps:
Figure 2. Starting SQL Server in Single user Mode
Figure 3. Starting SQL Server in Single user Mode
Note that step 2 refers to the Binn directory location. It can be different in your installation.
You can find the necessary directory by checking the Service tab of SQL Server service properties in SQL Server Configuration Manager (See Figure 4):
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