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sys.dm_io_virtual_file_stats (Transact-SQL)

Returns I/O statistics for data and log files. This dynamic management view replaces the fn_virtualfilestats function.

Applies to: SQL Server (SQL Server 2008 through current version).

sys.dm_io_virtual_file_stats ( 
{ database_id | NULL }
, { file_id | NULL }
)

database_id | NULL

ID of the database. database_id is int, with no default. Valid inputs are the ID number of a database or NULL. When NULL is specified, all databases in the instance of SQL Server are returned.

The built-in function DB_ID can be specified.

file_id | NULL

ID of the file. file_id is int, with no default. Valid inputs are the ID number of a file or NULL. When NULL is specified, all files on the database are returned.

The built-in function FILE_IDEX can be specified, and refers to a file in the current database.

Column name

Data type

Description

database_id

smallint

ID of database.

file_id

smallint

ID of file.

sample_ms

int

Number of milliseconds since the computer was started. This column can be used to compare different outputs from this function.

num_of_reads

bigint

Number of reads issued on the file.

num_of_bytes_read

bigint

Total number of bytes read on this file.

io_stall_read_ms

bigint

Total time, in milliseconds, that the users waited for reads issued on the file.

num_of_writes

bigint

Number of writes made on this file.

num_of_bytes_written

bigint

Total number of bytes written to the file.

io_stall_write_ms

bigint

Total time, in milliseconds, that users waited for writes to be completed on the file.

io_stall

bigint

Total time, in milliseconds, that users waited for I/O to be completed on the file.

size_on_disk_bytes

bigint

Number of bytes used on the disk for this file. For sparse files, this number is the actual number of bytes on the disk that are used for database snapshots.

file_handle

varbinary

Windows file handle for this file.

io_stall_queued_read_ms

bigint

Total IO latency introduced by IO resource governance for reads. Is not nullable. For more information, see sys.dm_resource_governor_resource_pools (Transact-SQL).

Applies to: SQL Server 2014 through SQL Server 2014.

io_stall_queued_write_ms

bigint

Total IO latency introduced by IO resource governance for writes. Is not nullable.

Applies to: SQL Server 2014 through SQL Server 2014.

Requires VIEW SERVER STATE permission. For more information, see Dynamic Management Views and Functions (Transact-SQL).

The following example returns statistics for the log file in the AdventureWorks2012 database.

SELECT * FROM sys.dm_io_virtual_file_stats(DB_ID(N'AdventureWorks2012'), 2);
GO
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