VTAM start options

Start options provide information about the conditions under which VTAM runs.

Start options also enable you to tailor VTAM to meet your needs each time VTAM is started. Many options can have defaults specified as start options, thus reducing the amount of coding required. Many start options can be dynamically modified and also displayed. You should be aware that some start options cannot be dynamically modified and require that VTAM be recycled. Start of change A complete description of start options is in z/OS Communications Server: SNA Resource Definition Reference. For a brief listing of the start options, see z/OS Communications Server: SNA Operation. End of change

To use a start option list, create a data set member named ATCSTRyy and put it in the VTAMLST partitioned data set. The yy value can be any two Start of change alphanumeric End of change characters and allows you to create different versions of the option list (ATCSTR00, ATCSTR01, ATCSTR02, and so forth) and therefore different versions of VTAM start options.

VTAM is started from the z/OS console or during z/OS system startup with the following command: Start of change

START NET,,,(LIST=yy)

When VTAM initializes, LIST=yy determines which option list to use. For example, if you specify LIST=01, VTAM uses ATCSTR01.

VTAM always attempts to locate ATCSTR00 first, regardless of the option list chosen. If ATCSTR00 does not exist, VTAM sends a warning message to the operator. To avoid receiving this message, create an ATCSTR00 file that contains only comments or start options that are always used for that particular VTAM.

Required VTAM start options

Some start options are required:

SSCPID: The SSCPID start option provides VTAM with a unique numeric identifier. The SSCPID value is used by some physical units to identify the VTAM with which it is in session. If you plan to expand or incorporate a single-domain network into a larger network, be sure that the value of SSCPID is unique for each host. The SSCPID value you specify must also be different from the SSCPIDs in other networks that can be in session with this host.
SSCPNAME: The SSCPNAME start option provides a unique name for VTAM. This option is required for a single-domain network, but is primarily used in multiple-domain and multiple-network environments to identify a particular VTAM. The SSCPNAME option must be different from the HOSTPU start option that identifies the physical unit within VTAM. Note: The SSCPNAME should match the name that is coded in the cross-domain resource manager major node for this VTAM.
NETID: The NETID start option provides VTAM with the network identifier. If you connect your VTAM to another network, the network identifiers must be unique.
HOSTSA: HOSTSA specifies the subarea number of this VTAM. (This option is not required for APPN nodes.)
HOSTPU: 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.