{"id":1034,"date":"2017-03-08T09:55:24","date_gmt":"2017-03-08T04:25:24","guid":{"rendered":"http:\/\/pramodsingla.com\/?p=1034"},"modified":"2017-03-08T09:55:24","modified_gmt":"2017-03-08T04:25:24","slug":"sql-server-tuning-find-io-wait-or-virtual-file-stats","status":"publish","type":"post","link":"https:\/\/pramodsingla.com\/?p=1034","title":{"rendered":"SQL Server Tuning: Find IO wait or Virtual File Stats"},"content":{"rendered":"

Problem Statement: <\/strong>Script to get the virtual file waits for IO waits.
\nSolution:<\/strong>\u00a0Virtual File waits are useful in identifying the IO waits occurring on any of the database file. This script is used along with SQL server wait stats script<\/a>\u00a0to understand the IO waits well.<\/h2>\n

SELECT<\/span>\u00a0Db_name<\/i><\/span>(<\/span>vfs<\/span>.<\/span>database_id<\/span>)<\/span>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0AS<\/span>\u00a0database_name<\/span>,<\/span>
\nvfs<\/span>.<\/span>database_id<\/span>,<\/span>
\nvfs<\/span>.<\/span>FILE_ID<\/span>,<\/span>
\nio_stall_read_ms<\/span>\u00a0\/<\/span>\u00a0NULLIF<\/i><\/span>(<\/span>num_of_reads<\/span>,<\/span>\u00a00<\/span>)<\/span>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0AS<\/span>\u00a0avg_read_latency<\/span>,<\/span>
\nio_stall_write_ms<\/span>\u00a0\/<\/span>\u00a0NULLIF<\/i><\/span>(<\/span>num_of_writes<\/span>,<\/span>\u00a00<\/span>)<\/span>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0AS<\/span>\u00a0avg_write_latency<\/span>,<\/span>
\nio_stall<\/span>\u00a0\/<\/span>\u00a0NULLIF<\/i><\/span>(<\/span>num_of_reads<\/span>\u00a0+<\/span>\u00a0num_of_writes<\/span>,<\/span>\u00a00<\/span>)<\/span>\u00a0AS<\/span>\u00a0avg_total_latency<\/span>,<\/span>
\nnum_of_bytes_read<\/span>\u00a0\/<\/span>\u00a0NULLIF<\/i><\/span>(<\/span>num_of_reads<\/span>,<\/span>\u00a00<\/span>)<\/span>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0AS<\/span>\u00a0avg_bytes_per_read<\/span>,<\/span>
\nnum_of_bytes_written<\/span>\u00a0\/<\/span>\u00a0NULLIF<\/i><\/span>(<\/span>num_of_writes<\/span>,<\/span>\u00a00<\/span>)<\/span>\u00a0\u00a0\u00a0\u00a0AS<\/span>\u00a0avg_bytes_per_write<\/span>
\n,<\/span>
\nvfs<\/span>.<\/span>io_stall<\/span>,<\/span>
\nvfs<\/span>.<\/span>num_of_reads<\/span>,<\/span>
\nvfs<\/span>.<\/span>num_of_bytes_read<\/span>,<\/span>
\nvfs<\/span>.<\/span>io_stall_read_ms<\/span>,<\/span>
\nvfs<\/span>.<\/span>num_of_writes<\/span>,<\/span>
\nvfs<\/span>.<\/span>num_of_bytes_written<\/span>,<\/span>
\nvfs<\/span>.<\/span>io_stall_write_ms<\/span>,<\/span>
\nsize_on_disk_bytes<\/span>\u00a0\/<\/span>\u00a01024<\/span>\u00a0\/<\/span>\u00a01024.<\/span>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0AS<\/span>\u00a0size_on_disk_mbytes<\/span>
\n,<\/span>
\nphysical_name<\/span>
\nFROM<\/span>\u00a0\u00a0\u00a0sys<\/span>.<\/span>dm_io_virtual_file_stats<\/b><\/span>(<\/span>NULL<\/span>,<\/span>\u00a0NULL<\/span>)<\/span>\u00a0AS<\/span>\u00a0vfs<\/span>
\nJOIN<\/span>\u00a0sys<\/span>.<\/span>master_files<\/span>\u00a0AS<\/span>\u00a0mf<\/span>
\nON<\/span>\u00a0vfs<\/span>.<\/span>database_id<\/span>\u00a0=<\/span>\u00a0mf<\/span>.<\/span>database_id<\/span>
\nAND<\/span>\u00a0vfs<\/span>.<\/span>FILE_ID<\/span>\u00a0=<\/span>\u00a0mf<\/span>.<\/span>FILE_ID<\/span>
\nORDER<\/span>\u00a0\u00a0BY<\/span>\u00a0avg_total_latency<\/span>\u00a0DESC<\/span><\/p><\/blockquote>\n","protected":false},"excerpt":{"rendered":"

Problem Statement: Script to get the virtual file waits for IO waits. Solution:\u00a0Virtual File waits are useful in identifying the[…]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"om_disable_all_campaigns":false,"_mi_skip_tracking":false,"_monsterinsights_sitenote_active":false,"_monsterinsights_sitenote_note":"","_monsterinsights_sitenote_category":0},"categories":[23,29],"tags":[75,104,171,187],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/pramodsingla.com\/index.php?rest_route=\/wp\/v2\/posts\/1034"}],"collection":[{"href":"https:\/\/pramodsingla.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/pramodsingla.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/pramodsingla.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/pramodsingla.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=1034"}],"version-history":[{"count":0,"href":"https:\/\/pramodsingla.com\/index.php?rest_route=\/wp\/v2\/posts\/1034\/revisions"}],"wp:attachment":[{"href":"https:\/\/pramodsingla.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=1034"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/pramodsingla.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=1034"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/pramodsingla.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=1034"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}