This document describes the "delete 20000 sessions alarm that might appear on the Cisco Secure Access Control System (ACS) 5.x dashboard.
Note: This content was created by Dragana Radmilo, Cisco TAC Engineer.
Q. What is the "delete 20000 sessions" alarm I see on my ACS 5.x dashboard?
A. This alert is informational and is generated because the ACS View keeps track of authentication sessions.
The ACS View maintains all the sessions (RADIUS/TACACS Authentication/Authorization/Accounting). It can keep only 250,000 sessions at a time. Whenever it crosses 250k, it will try to delete 20k sessions, and will send an alarm (the one that you see on the ACS Dashboard).
The ACS normally keeps track of the session authentications by following accounting records ACCOUNT_START and ACCOUNT_STOP. However, if ACS View does not get ACCOUNT_STOP records, the number of sessions will not be decreased. As a result, any active sessions for which the ACS View does not receive an ACCOUNT_STOP will remain and then expire after two days.
This is covered in Cisco bug ID CSCtj69797 ( registered customers only) .
Note: These messages are purely informational and do not impact authentication.