The NOTES.INI parameter LOG_SESSIONS specifies whether individual sessions are recorded in the log file and displayed on the console. The parameter LOG_SESSIONS has two values as mentioned in the regular standard documentation, 0 and 1. As an example as we look in the IBM Domino Administrator 9.0.1 Social Edition Help database, only the values 0 and 1 are documented.
However, there is also a not so well documented value 2 for the parameter LOG_SESSIONS. LOG_SESSIONS=2 will print the Session Id, IP, Authenticated and (client/server)/pass-thru.
It can be set dynamically with set config log_sessions=2 or in the Domino NOTES.INI in the Configuration document. Value 2 is available since Domino 8.5.1.
0 = Do not log individual sessions
1 = Log individual sessions
2 = Log individual session with IP address and other information
Sample output for LOG_SESSIONS=1:
05/10/2018 13:15:05 Opened session for server01/domino (Release 9.0.1)
Sample output for LOG_SESSIONS=2:
05/10/2018 12:57:03 Opened session for 'server01/domino (Release 9.0.1) SessId 000E0FAE Ip '127.0.0.1' 'Auth' 'S'
05-10-2018 12:57:06 Closed session for 'username' SessId 006B0989 Databases accessed: 1 Documents read: 0 Documents written: 0 Transactions: 33