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As per explaination given on MSDN at link http://msdn.microsoft.com/en-us/library/ms177648.aspx I am not able to understand the meaning of Reads and Writes fully.whether it is physical or logical or database Reads and Writes. Please help me out in this regards
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The I/O from an instance of the SQL Server Database Engine includes logical and physical reads. A logical read occurs every time the Database Engine requests a page from the buffer cache. If the page is not currently in the buffer cache, a physical read first copies the page from disk into the cache.
dm_exec_requests returns data for all databases on the server. If the table contains database specific data, then it will include a database_id field.
Dynamic management views and functions return server state information that can be used to monitor the health of a server instance, diagnose problems, and tune performance.
The execution plan in XML format for the slow-running query or batch is contained in the query_plan column of the table returned by sys. dm_exec_query_plan .
It's number of physical reads/writes of 8k blocks. So if you multiply it by 8 you will get number of kilobytes that was read/written.
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Martin answered your question...the logical_reads column corresponds to logical reads (i.e. requests that can be fulfilled by data currently available in the buffer cache) while reads corresponds to physical reads (i.e. requests for data that isn't currently in the buffer cache and requires a read from the relevant data file on disk).
A write in SQL Server modifies the page in memory; modified pages are marked as dirty and written to disk by asynchronous processes (also what Martin said).
Just to add, all of these figures represent number of pages, not rows.
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