As awr is enabled when oracle is installed with database creation.And id I don't purchase daigonistic pack and if I use it like for awr reports,how does oracle corp. will come to know that i am using awr reports.
I thought awr report is inbuilt with oracle binaries and it is free.You will find that a lot of extra cost features are built-in and are NOT free - partitioning is one such extra cost option. As the DBA (or owner) of that database, it is your responsibility to turn off what was not purchased and not use what was not purchased.
The first time you log into Enterprise Manager Database Control as the SYSMAN user, you will be prompted to disable unlicensed items. Disabling the Diagnostic Pack license does not disable AWR logging - the data is still captured to the various tables. But you cannot legally query these tables without a Diagnostic Pack license - just querying the tables or views based on those tables could/will update the corresponding row in the DBA_FEATURE_USAGE_STATISTICS view.
SELECT NAME, VERSION, DETECTED_USAGES, TOTAL_SAMPLES, CURRENTLY_USED, FIRST_USAGE_DATE, LAST_USAGE_DATE, LAST_SAMPLE_DATE FROM DBA_FEATURE_USAGE_STATISTICS;