Where is the Session timeout set??

Hello,

I get the following error from mainframe, if I give an interval of 15 mins while using the applicaiton:

The transaction failed with no message. : Transaction=EVS1Adapter.Transactions:MISCOPYBOOKRXCO029Error ID = ( 800405a1 / 0 )<<<<<<,errorMsg=SystemException:Mainframe Transaction invoke failed, name=EVS1Adapter.Transactions:MISCOPYBOOKRXCO029,
The Host Communication Subsystem cancelled a transaction request because the session was disconnected from the host.
The Host Communication Subsystem cancelled a transaction request because the session was disconnected from the host.

Now, I wonder where is this session time set…is it in IS or in mainframe system.

Thanks,
Sunny