VTAM® also supports the use of a switched connection to a link-attached NCP. A switched link can be used to load, activate, or dump the NCP using normal operator commands. No VTAM definition changes are required, but because NCP does not support a password and encryption process, no call security verification is supported. You cannot code the PRTCT password if this support is used to load and activate an NCP over a switched link because a VTAM is required at the other link station to perform the encryption process.

For example, in Figure 1, if VTAM2 fails, VTAM1 can reload and activate NCP2 using a switched connection. However, you cannot use call security verification because VTAM2 is not available to perform the encryption process. Therefore, you cannot code the PRTCT password operand on the switched definition for the PU type 4 connection; if you do, the contact process over the switched link fails.

Before communication, however, information must be exchanged to determine whether the connection can be established. VTAM uses the IDNUM value coded on the PU definition statement to determine if the connection is to a defined NCP subarea node. The IDNUM specification must match the IDNUM specification coded in the NCP on the SWMMT definition statement. For more information about this type of connection, see Enhanced remote controller support.