Maximum session of the whole system can be increased at:

Administration   >>> Appliances   >>> click on the appliance >>> Configuration  >>> come to others tab >>>system >>> configuration

Configure max session per tenant at:

Administration   >>> Appliances   >>> click on the appliance >>> Configuration  >>> come to others tab >>>Organisation >>> Limits

If you want to configure more than 1 million sessions, you must first configure globally under the system and then increase it at the organization level.  

Please note that updating the max-session limit would require a restart of the services.

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