SYS1.VTAMLST

SYS1.VTAMLST is the z/OS® Communications Server definition library, which consists of files containing the definitions for network resources and start options. It is a required partitioned data set, and you need to allocate it on a direct-access volume before you file z/OS Communications Server network definitions.

This data set can be allocated and cataloged at either of these times:
  • Any time before its initial use. Run the IEHPROGM utility program or the IEBUPDTE utility program.
  • When the data set is first used. Code the appropriate job control language (JCL).

To prepare the SYS1.VTAMLST data set, do these steps:

  1. Allocate space to accommodate the filing of definitions for major nodes and anticipated sets of start options. The amount needed depends on the number of nodes and operands used and on the number of start options. See z/OS Communications Server: SNA Network Implementation Guide for more information about start options.
  2. Specify the DD name for SYS1.VTAMLST as VTAMLST. You should specify these DCB subparameters: 
    RECFM=FB,LRECL=80,BLKSIZE=any multiple of 80
  3. Code LABEL=RETPD=0 on all DD statements for SYS1.VTAMLST. If you do not, an operator awareness message requiring a reply might be generated.
  4. If you generate a NEWDEFN data set as part of NCP generation processing, ensure that it is loaded into SYS1.VTAMLST prior to activating the NCP. Failure to do so can cause serious problems. z/OS Communications Server uses the NCP source, in addition to the NCP load module and RRT, when loading and activating communication controllers. SYS1.VTAMLST must contain either the source used as input to the NCP generation process, if a NEWDEFN data set was not created, or the NEWDEFN data set, if one was created. For more information about NEWDEFN, see NCP, SSP, and EP Generation and Loading Guide.
  5. If you are configuring z/OS Communications Server as an APPN node (or plan to do so in the future), copy the IBM®-supplied APPN class of service (COS) definitions and APPN transmission group (TG) profiles from ASAMPLIB into SYS1.VTAMLST. Three sets of IBM-supplied COS definitions are available to enable z/OS Communications Server to select an optimal route for a session:
    • COSAPPN

      The definitions in COSAPPN are appropriate for most sessions.

    • ISTACST2

      The definitions in ISTACST2 are most useful for multiple types of connections with different TG characteristics. For example, the definitions are useful when channel-to-channel, token ring network, FDDI LAN, or ATM are used in the network.

    • ISTACST3

      The definitions in ISTACST3 are designed to enable z/OS Communications Server to select an optimal route for a session when connections used in the network include those with high speed link characteristics such as FICON®, Gigabit Ethernet, and HiperSockets.

    One of these three sets of APPN COS definitions is required if z/OS Communications Server is configured as an APPN node. To use COSAPPN, ISTACST2, or ISTACST3, you must copy the appropriate set of definitions into SYS1.VTAMLST at z/OS Communications Server installation, and then activate the member in which the definitions reside. You can copy more than one set of definitions into SYS1.VTAMLST, but you can have only one set active at any time. For additional information about selecting and activating the best APPN COS definitions for your network, see the discussion about the IBM-supplied default classes of service in z/OS Communications Server: SNA Network Implementation Guide.

    The IBM-supplied TG profiles are in IBMTGPS in ASAMPLIB. IBMTGPS is not required, but you should include it. You can copy IBMTGPS into SYS1.VTAMLST; it is automatically activated when z/OS Communications Server is initialized.

Guidelines:
  • Because CP-CP session paths might include subarea VRs, it is also strongly recommended that you update your logon mode tables (including the IBM-supplied logon mode table, ISTINCLM) to include an appropriate COS= value on the CPSVCMG and CPSVRMGR mode table entries. Otherwise, a blank COS name will be used to determine the subarea VR and transmission priority that will be used for the VR portion of the CP-CP session path.
  • You can modify SYS1.VTAMLST, but you need to be very careful about the relationship between z/OS Communications Server and NCP definition statements. For example, changing a VTAMLST member without changing a corresponding NCP definition statement can cause serious errors that are difficult to diagnose.