v$sesstat records the cumulative stat for each session. And each row uniquely identified by sid. So the question is what is a session with sid 100 logout, and another new session is assigned the sid to 100. Will the v$sessat calculate the stat for a new session after it purge the stats for that sid. That is to say, does the stats include the stats from the first session? If the first session(already log off) with sid=100 created 10M redo size and the second session with sid=100 create 10M redo size, will the v$sesstat show that the redo sid for sid is 10M+10M=20M?