MSDB is part of system databases which is necessary for sql server to perform sql server jobs related tasks. MSDB database is used to stores sql jobs and database backup related data in sql server. Sql server agent makes use of MSDB database for scheduling sql jobs and alerts. Whenever we install sql server, MSDB comes as default database with other system database.
Physical file location is “C:\Program Files\Microsoft SQL Server\MSSQL.1\MSSQL\DATA” with sql server primary data file as msdbdata.mdf and msdblog.ldf as transaction log file.
If we set data file to auto growth then it will grow up to total size of disk whereas transaction log will grow up to maximum 2 TB.
A lots of operations can not be performed on MSDB like dropping database,database mirroring configuration, setting database in offline mode and collation.