Hi Hitesh,
The only option you have is to download the .CSV files and import it into spreadsheets by using most popular spreadsheet application software. You can also use a third-party reporting tool to manage report data. For example, aaa-reports! by Extraxi supports ACS.
To download a CSV report:
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# click Reports and Activity.
# Click the CSV report filename that you want to download.
# In the right pane of the browser, click Download.
# You can easily analyse the logs in Microsoft excel
How to filter and analyze logs ( with Regular Expression Syntax Definitions):
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http://www.cisco.com/en/US/partner/docs/net_mgmt/cisco_secure_access_control_server_for_windows/4.2/user/guide/LgsRpts.html#wp632961
For downloading third party application
http://www.extraxi.com/
For more info, you can download the user guide:
http://www.extraxi.com/PDFs/aaa-reports%20sales%20proposal%20-%20customer.pdf
HTH
Regards,
JK
~Jatin