Performance Tuning with SQL Server Dynamic Management Views

Chapter 3: Query Plan Metadata
However, other attributes are important, too, the values for which are stored in the sys.
dm_exec_plan_attributes function, described by Books Online as follows:
Returns one row per plan attribute for the plan specified by the plan handle. You can use this table-valued
function to get details about a particular plan, such as the cache key values or the number of current
simultaneous executions of the plan.
Like sys.dm_exec_query_plan, sys.dm_exec_plan_attributes takes a
plan_handle as a parameter and returns the following columns:
• attribute – name of the attribute
• value – the current value assigned to the attribute
• is_cache_key – indicates if the attribute is part of how SQL Server resolves the plan;
A value of 1 indicates that it is, and 0 that it is not.
This DMV returns one row per plan attribute, and available attributes include:
• set_options – the options values (the ones that can be found using @@options,
such as SET NOCOUNT) that were in use when the plan was built
• date_format – the date format of the connection that created the plan
• inuse_exec_context – the number of currently executing batches that are
using the plan.
If the value of is_cache_key is 1 for a given attribute, that attribute forms part of the
"key" that is used when SQL Server searches the cache for a suitable plan. During the
process of checking the cache for a match, the text of a submitted query is compared to
the text of other queries that have been executed and for which a plan is stored. Even if
the text of the queries matches exactly, the submitted query's attributes would also need
to match exactly those for the cached plan, for every attribute with a value of 1 for the
is_cache_key column in sys.dm_exec_plan_attributes.
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