SELECT TOP(100) [text], cp.size_in_bytes
FROM sys.dm_exec_cached_plans AS cp
CROSS APPLY sys.dm_exec_sql_text(plan_handle) 
WHERE cp.cacheobjtype = 'Compiled Plan' 
AND cp.objtype = 'Adhoc' 
AND cp.usecounts = 1
ORDER BY cp.size_in_bytes DESC;

List of single-use, ad-hoc queries that are bloating the plan cache

sql

SQL