Validation Period Setting for Persistent Session

Document ID : KB000098321
Last Modified Date : 25/07/2018
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Question: we have one realm with the below settings

persistent Session: persistent 
validation period: Enabled 
hours: 0 
Minutes: 0 
Seconds: 0 

what does it mean when set hour/min/sec/ to 0? does it mean webagent will validate user session for every request? or it means it will never validate user session? 
If the validation period is set to zero, then indefinitely the authentication is done from cache and no calls are made to the policy server.
The Validation Period value must be greater than zero.
The session validation period must be less than the specified Idle Timeout value.