This article applies to DPA 8.0 and later.
DPA collects SQL execution statistics when monitoring SQL Server 2005 and later. If certain SQL statements are missing SQL execution statistics, it may be because:
SQL statistics collection was turned off for the monitored database instance.
The SQL buffer cache on the monitored database is too small or too many distinct SQL statements are executed on the monitored database. SQL statistics are queried every 10 minutes and compared to the previously queried values. If the same SQL statement cannot be found in the buffer cache after 10 minutes, no SQL statistics can be calculated for that SQL statement.
The SQL statement is contained within a stored procedure that has been compiled with the RECOMPILE option, or the SQL statement uses the RECOMPILE query hint. This causes SQL Server to recompile the stored procedure or statement before every execution and to not store the SQL plan in the buffer cache. If the SQL plan for the statement is not stored in the buffer cache, SQL Server does not track SQL statistics for that statement.