> # Allowing the Host to Control the Timestamp

> By default, the clock in each VSAN is the same as the switch hardware clock. Each VSAN in a Cisco MDS 9000 Family switch represents a virtual director. The clock and time present in each virtual director can be different.To maintain separate clocks for each VSAN, the Cisco NX-OS software maintains the difference of the VSAN-specific clock and the hardware-based director clock. When a host (mainframe) sets the time, the Cisco NX-OS software updates this difference between the clocks. When a host reads the clock, it computes the difference between the VSAN-clock and the current director hardware clock and presents a value to the mainframe.

> ## Detailed Steps

> To configure host (mainframe) control for the VSAN time stamp, follow these steps:

> 1. Choose VSAN > FICON.

> You see a list of switches under the Control tab in the Information pane.

> 2. Click the VSANs tab.

> You see the FICON VSAN configuration information in the Information pane.

> 3. Check the Host Can Sync Time checkbox to allow the mainframe to set the system time on the switch.
> 4. Click the Apply Changes icon to save these changes.

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