SQL System Database

Microsoft sqlserver has four types of system databases:
1. master database
The master database records all system-level information of the sqlserver system. It records all logon accounts and system configuration settings. The master database is such a database that records all other databases, including the location of database files.
The master database records the initialization information of sqlserver. It always has an available backup of the latest master database.
2. tempdb Database
The tempdb database stores all temporary tables and temporary stored procedures. It also meets any other temporary storage requirements,
For example, the worksheet generated by sqlserver is stored. The tempdb database is a global resource. All temporary tables and stored procedures of users connected to the system are stored in the database. The tempdb database is re-created every time SQL Server is started. Therefore, the database is always clean when the system is started. Temporary tables and stored procedures are automatically removed when the connection is disconnected, and no connections are active when the system is closed, therefore, no content in the tempdb database is saved from one session of sqlserver to another.
By default, the tempdb database increases automatically when sqlserver is running as needed. However, unlike other databases, each time the database engine is started, it is reset to its initial size. If the size defined for the tempdb database is small, automatically increasing the size of the tempdb database to the size required to support the workload may become part of the system's processing load. To avoid this overhead, you can use alter database to increase the size of the tempdb database.
3. model database
The model database is used as a template for all databases created on the system. When the create database Statement is issued, the first part of the new database is created by copying the content in the model database, and the rest is filled with blank pages. Since tempcreates A tempdb database every time it is started, the model database must always exist in sqlserver.
4. MSDB Database
MSDB database for SQL Server proxyProgramUsed to schedule alarms and jobs and record operators.