The HOSTPU start option is recommended (but not required) for identifying VTAM® to the network.

Use the HOSTPU start option to assign a user-defined name to the VTAM host physical unit. The default name for the host physical unit is ISTPUS. Because the NetView® program uses this name to associate network information to a specific VTAM, you should make sure that this name is meaningful and unique throughout the network.

For start options you are not required to code, VTAM uses the default values. You can override any start option value when VTAM is started or enter new start option values at the operator console.