C# application profiling gives different results

Hi,

I'm new to profiling and dottrace profiler. I'm trying to profile a C# application which connects to an SQLite database and retrieve data. The database contains 146856400 rows and the select query retrieves 428800 rows after execution.

On the first execution the main thread takes 246686 ms

On second execution of the same code the main thread takes only 4296 ms




After restarting the system

On the first execution the main thread takes 244533 ms
On the second execution of the same code the main thread takes only 4053 ms


Questions:

1) Why is there a hugh difference between the first execution timing and the second execution timing
2) After restarting the system why I'm not getting the same results.

Pls help