In addition to having the use of log files and Transact-SQL statements, you will find a set of built-in functions that return system information. Here’s an overview of key built-in functions and their usages. The values returned by these functions are cumulative from the time SQL Server was last started.
||Returns the number of connections or attempted connections
||select @@connections as 'Total Login Attempts'
||Returns CPU processing time in milliseconds for SQL Server activity
||select @@cpu_busy as 'CPU Busy', getdate() as 'Since'
||Returns SQL Server idle time in milliseconds
||select @@idle as 'Idle Time', getdate() as 'Since'
||Returns I/O processing time in milliseconds
||select @@io_busy as 'IO Time', getdate() as 'Since' for SQL Server
||Returns the number of input packets read from the network by SQL Server
||select @@pack_received as 'Packets Received'
||Returns the number of output packets written to the network by SQL Server
||select @@pack_sent as 'Packets Sent'
||Returns the number of network packet errors for SQL Server connections
||select @@packet_errors as 'Packet Errors'
||Returns the number of microseconds per CPU clock tick
||select @@timeticks as 'Clock Ticks'
||Returns the number of disk read/write errors encountered by SQL Server
||select @@total_errors as 'Total Errors', getdate() as 'Since'
||Returns the number of disk reads by SQL Server
||select @@total_read as 'Reads', getdate() as 'Since'
||Returns the number of disk writes by SQL Server
||select @@total_write as 'Writes', getdate() as 'Since'
||Returns input/output statistics for data and log files
||select * from fn_virtualfilestats(null,null)